diff --git a/docs/mcp-elements.md b/docs/mcp-elements.md
index 911b3d52..1bb2690d 100644
--- a/docs/mcp-elements.md
+++ b/docs/mcp-elements.md
@@ -154,16 +154,21 @@ public function getMultipleContent(): array
 
 #### Error Handling
 
-Tools can throw exceptions which are automatically converted to proper JSON-RPC error responses:
+Tool handlers can throw any exception, but the type determines how it's handled:
+
+- **`ToolCallException`**: Converted to JSON-RPC response with `CallToolResult` where `isError: true`, allowing the LLM to see the error message and self-correct
+- **Any other exception**: Converted to JSON-RPC error response, but with a generic error message
 
 ```php
+use Mcp\Exception\ToolCallException;
+
 #[McpTool]
 public function divideNumbers(float $a, float $b): float
 {
     if ($b === 0.0) {
-        throw new \InvalidArgumentException('Division by zero is not allowed');
+        throw new ToolCallException('Division by zero is not allowed');
     }
-    
+
     return $a / $b;
 }
 
@@ -171,14 +176,15 @@ public function divideNumbers(float $a, float $b): float
 public function processFile(string $filename): string
 {
     if (!file_exists($filename)) {
-        throw new \InvalidArgumentException("File not found: {$filename}");
+        throw new ToolCallException("File not found: {$filename}");
     }
-    
+
     return file_get_contents($filename);
 }
 ```
 
-The SDK will convert these exceptions into appropriate JSON-RPC error responses that MCP clients can understand.
+**Recommendation**: Use `ToolCallException` when you want to communicate specific errors to clients. Any other exception will still be converted to JSON-RPC compliant errors but with generic error messages.
+
 
 ## Resources
 
@@ -298,24 +304,31 @@ public function getMultipleResources(): array
 
 #### Error Handling
 
-Resource handlers can throw exceptions for error cases:
+Resource handlers can throw any exception, but the type determines how it's handled:
+
+- **`ResourceReadException`**: Converted to JSON-RPC error response with the actual exception message
+- **Any other exception**: Converted to JSON-RPC error response, but with a generic error message
 
 ```php
+use Mcp\Exception\ResourceReadException;
+
 #[McpResource(uri: 'file://{path}')]
 public function getFile(string $path): string
 {
     if (!file_exists($path)) {
-        throw new \InvalidArgumentException("File not found: {$path}");
+        throw new ResourceReadException("File not found: {$path}");
     }
-    
+
     if (!is_readable($path)) {
-        throw new \RuntimeException("File not readable: {$path}");
+        throw new ResourceReadException("File not readable: {$path}");
     }
-    
+
     return file_get_contents($path);
 }
 ```
 
+**Recommendation**: Use `ResourceReadException` when you want to communicate specific errors to clients. Any other exception will still be converted to JSON-RPC compliant errors but with generic error messages.
+
 ## Resource Templates
 
 Resource templates are **dynamic resources** that use parameterized URIs with variables. They follow all the same rules
@@ -449,6 +462,8 @@ public function explicitMessages(): array
 }
 ```
 
+The SDK automatically validates that all messages have valid roles and converts the result into the appropriate MCP prompt message format.
+
 #### Valid Message Roles
 
 - **`user`**: User input or questions  
@@ -456,33 +471,35 @@ public function explicitMessages(): array
 
 #### Error Handling
 
-Prompt handlers can throw exceptions for invalid inputs:
+Prompt handlers can throw any exception, but the type determines how it's handled:
+- **`PromptGetException`**: Converted to JSON-RPC error response with the actual exception message
+- **Any other exception**: Converted to JSON-RPC error response, but with a generic error message
 
 ```php
+use Mcp\Exception\PromptGetException;
+
 #[McpPrompt]
 public function generatePrompt(string $topic, string $style): array
 {
     $validStyles = ['casual', 'formal', 'technical'];
-    
+
     if (!in_array($style, $validStyles)) {
-        throw new \InvalidArgumentException(
+        throw new PromptGetException(
             "Invalid style '{$style}'. Must be one of: " . implode(', ', $validStyles)
         );
     }
-    
+
     return [
         ['role' => 'user', 'content' => "Write about {$topic} in a {$style} style"]
     ];
 }
 ```
 
-The SDK automatically validates that all messages have valid roles and converts the result into the appropriate MCP prompt message format.
+**Recommendation**: Use `PromptGetException` when you want to communicate specific errors to clients. Any other exception will still be converted to JSON-RPC compliant errors but with generic error messages.
 
 ## Completion Providers
 
-Completion providers help MCP clients offer auto-completion suggestions for Resource Templates and Prompts. Unlike Tools
-and static Resources (which can be listed via `tools/list` and `resources/list`), Resource Templates and Prompts have
-dynamic parameters that benefit from completion hints.
+Completion providers help MCP clients offer auto-completion suggestions for Resource Templates and Prompts. Unlike Tools and static Resources (which can be listed via `tools/list` and `resources/list`), Resource Templates and Prompts have dynamic parameters that benefit from completion hints.
 
 ### Completion Provider Types
 
diff --git a/examples/http-client-communication/server.php b/examples/http-client-communication/server.php
index 2acce334..8191a8e2 100644
--- a/examples/http-client-communication/server.php
+++ b/examples/http-client-communication/server.php
@@ -14,6 +14,7 @@
 
 use Http\Discovery\Psr17Factory;
 use Laminas\HttpHandlerRunner\Emitter\SapiEmitter;
+use Mcp\Exception\ToolCallException;
 use Mcp\Schema\Content\TextContent;
 use Mcp\Schema\Enum\LoggingLevel;
 use Mcp\Schema\JsonRpc\Error as JsonRpcError;
@@ -64,7 +65,7 @@ function (string $projectName, array $milestones, ClientGateway $client): array
             );
 
             if ($response instanceof JsonRpcError) {
-                throw new RuntimeException(sprintf('Sampling request failed (%d): %s', $response->code, $response->message));
+                throw new ToolCallException(sprintf('Sampling request failed (%d): %s', $response->code, $response->message));
             }
 
             $result = $response->result;
diff --git a/examples/http-discovery-userprofile/McpElements.php b/examples/http-discovery-userprofile/McpElements.php
index e763891a..933bd51e 100644
--- a/examples/http-discovery-userprofile/McpElements.php
+++ b/examples/http-discovery-userprofile/McpElements.php
@@ -16,7 +16,8 @@
 use Mcp\Capability\Attribute\McpResource;
 use Mcp\Capability\Attribute\McpResourceTemplate;
 use Mcp\Capability\Attribute\McpTool;
-use Mcp\Exception\InvalidArgumentException;
+use Mcp\Exception\PromptGetException;
+use Mcp\Exception\ResourceReadException;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -48,7 +49,7 @@ public function __construct(
      *
      * @return User user profile data
      *
-     * @throws InvalidArgumentException if the user is not found
+     * @throws ResourceReadException if the user is not found
      */
     #[McpResourceTemplate(
         uriTemplate: 'user://{userId}/profile',
@@ -62,7 +63,7 @@ public function getUserProfile(
     ): array {
         $this->logger->info('Reading resource: user profile', ['userId' => $userId]);
         if (!isset($this->users[$userId])) {
-            throw new InvalidArgumentException("User profile not found for ID: {$userId}");
+            throw new ResourceReadException("User not found for ID: {$userId}");
         }
 
         return $this->users[$userId];
@@ -130,7 +131,7 @@ public function testToolWithoutParams(): array
      *
      * @return array<string, string>[] prompt messages
      *
-     * @throws InvalidArgumentException if user not found
+     * @throws PromptGetException if user not found
      */
     #[McpPrompt(name: 'generate_bio_prompt')]
     public function generateBio(
@@ -140,7 +141,7 @@ public function generateBio(
     ): array {
         $this->logger->info('Executing prompt: generate_bio', ['userId' => $userId, 'tone' => $tone]);
         if (!isset($this->users[$userId])) {
-            throw new InvalidArgumentException("User not found for bio prompt: {$userId}");
+            throw new PromptGetException("User not found for bio prompt: {$userId}");
         }
         $user = $this->users[$userId];
 
diff --git a/examples/stdio-cached-discovery/CachedCalculatorElements.php b/examples/stdio-cached-discovery/CachedCalculatorElements.php
index 2d5249df..1da3d277 100644
--- a/examples/stdio-cached-discovery/CachedCalculatorElements.php
+++ b/examples/stdio-cached-discovery/CachedCalculatorElements.php
@@ -14,6 +14,7 @@
 namespace Mcp\Example\StdioCachedDiscovery;
 
 use Mcp\Capability\Attribute\McpTool;
+use Mcp\Exception\ToolCallException;
 
 /**
  * Example MCP elements for demonstrating cached discovery.
@@ -39,7 +40,7 @@ public function multiply(int $a, int $b): int
     public function divide(int $a, int $b): float
     {
         if (0 === $b) {
-            throw new \InvalidArgumentException('Division by zero is not allowed');
+            throw new ToolCallException('Division by zero is not allowed');
         }
 
         return $a / $b;
diff --git a/examples/stdio-discovery-calculator/McpElements.php b/examples/stdio-discovery-calculator/McpElements.php
index 71aea372..21330313 100644
--- a/examples/stdio-discovery-calculator/McpElements.php
+++ b/examples/stdio-discovery-calculator/McpElements.php
@@ -13,6 +13,7 @@
 
 use Mcp\Capability\Attribute\McpResource;
 use Mcp\Capability\Attribute\McpTool;
+use Mcp\Exception\ToolCallException;
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 
@@ -44,10 +45,10 @@ public function __construct(
      * @param float  $b         the second operand
      * @param string $operation the operation ('add', 'subtract', 'multiply', 'divide')
      *
-     * @return float|string the result of the calculation, or an error message string
+     * @return float the result of the calculation
      */
     #[McpTool(name: 'calculate')]
-    public function calculate(float $a, float $b, string $operation): float|string
+    public function calculate(float $a, float $b, string $operation): float
     {
         $this->logger->info(\sprintf('Calculating: %f %s %f', $a, $operation, $b));
 
@@ -65,16 +66,16 @@ public function calculate(float $a, float $b, string $operation): float|string
                 break;
             case 'divide':
                 if (0 == $b) {
-                    return 'Error: Division by zero.';
+                    throw new ToolCallException('Division by zero is not allowed.');
                 }
                 $result = $a / $b;
                 break;
             default:
-                return "Error: Unknown operation '{$operation}'. Supported: add, subtract, multiply, divide.";
+                throw new ToolCallException("Unknown operation '{$operation}'. Supported: add, subtract, multiply, divide.");
         }
 
         if (!$this->config['allow_negative'] && $result < 0) {
-            return 'Error: Negative results are disabled.';
+            throw new ToolCallException('Negative results are disabled.');
         }
 
         return round($result, $this->config['precision']);
diff --git a/src/Capability/Registry.php b/src/Capability/Registry.php
index 94db079f..3a13c323 100644
--- a/src/Capability/Registry.php
+++ b/src/Capability/Registry.php
@@ -23,6 +23,9 @@
 use Mcp\Event\ResourceTemplateListChangedEvent;
 use Mcp\Event\ToolListChangedEvent;
 use Mcp\Exception\InvalidCursorException;
+use Mcp\Exception\PromptNotFoundException;
+use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Exception\ToolNotFoundException;
 use Mcp\Schema\Page;
 use Mcp\Schema\Prompt;
 use Mcp\Schema\Resource;
@@ -209,43 +212,41 @@ public function clear(): void
         }
     }
 
-    public function getTool(string $name): ?ToolReference
+    public function getTool(string $name): ToolReference
     {
-        return $this->tools[$name] ?? null;
+        return $this->tools[$name] ?? throw new ToolNotFoundException($name);
     }
 
     public function getResource(
         string $uri,
         bool $includeTemplates = true,
-    ): ResourceReference|ResourceTemplateReference|null {
+    ): ResourceReference|ResourceTemplateReference {
         $registration = $this->resources[$uri] ?? null;
         if ($registration) {
             return $registration;
         }
 
-        if (!$includeTemplates) {
-            return null;
-        }
-
-        foreach ($this->resourceTemplates as $template) {
-            if ($template->matches($uri)) {
-                return $template;
+        if ($includeTemplates) {
+            foreach ($this->resourceTemplates as $template) {
+                if ($template->matches($uri)) {
+                    return $template;
+                }
             }
         }
 
         $this->logger->debug('No resource matched URI.', ['uri' => $uri]);
 
-        return null;
+        throw new ResourceNotFoundException($uri);
     }
 
-    public function getResourceTemplate(string $uriTemplate): ?ResourceTemplateReference
+    public function getResourceTemplate(string $uriTemplate): ResourceTemplateReference
     {
-        return $this->resourceTemplates[$uriTemplate] ?? null;
+        return $this->resourceTemplates[$uriTemplate] ?? throw new ResourceNotFoundException($uriTemplate);
     }
 
-    public function getPrompt(string $name): ?PromptReference
+    public function getPrompt(string $name): PromptReference
     {
-        return $this->prompts[$name] ?? null;
+        return $this->prompts[$name] ?? throw new PromptNotFoundException($name);
     }
 
     public function getTools(?int $limit = null, ?string $cursor = null): Page
diff --git a/src/Capability/Registry/ReferenceProviderInterface.php b/src/Capability/Registry/ReferenceProviderInterface.php
index 2f60014b..0af66e1f 100644
--- a/src/Capability/Registry/ReferenceProviderInterface.php
+++ b/src/Capability/Registry/ReferenceProviderInterface.php
@@ -11,6 +11,9 @@
 
 namespace Mcp\Capability\Registry;
 
+use Mcp\Exception\PromptNotFoundException;
+use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Exception\ToolNotFoundException;
 use Mcp\Schema\Page;
 
 /**
@@ -23,23 +26,31 @@ interface ReferenceProviderInterface
 {
     /**
      * Gets a tool reference by name.
+     *
+     * @throws ToolNotFoundException
      */
-    public function getTool(string $name): ?ToolReference;
+    public function getTool(string $name): ToolReference;
 
     /**
      * Gets a resource reference by URI (includes template matching if enabled).
+     *
+     * @throws ResourceNotFoundException
      */
-    public function getResource(string $uri, bool $includeTemplates = true): ResourceReference|ResourceTemplateReference|null;
+    public function getResource(string $uri, bool $includeTemplates = true): ResourceReference|ResourceTemplateReference;
 
     /**
      * Gets a resource template reference by URI template.
+     *
+     * @throws ResourceNotFoundException
      */
-    public function getResourceTemplate(string $uriTemplate): ?ResourceTemplateReference;
+    public function getResourceTemplate(string $uriTemplate): ResourceTemplateReference;
 
     /**
      * Gets a prompt reference by name.
+     *
+     * @throws PromptNotFoundException
      */
-    public function getPrompt(string $name): ?PromptReference;
+    public function getPrompt(string $name): PromptReference;
 
     /**
      * Gets all registered tools.
diff --git a/src/Exception/PromptGetException.php b/src/Exception/PromptGetException.php
index 8970ea58..7eec0daf 100644
--- a/src/Exception/PromptGetException.php
+++ b/src/Exception/PromptGetException.php
@@ -11,17 +11,9 @@
 
 namespace Mcp\Exception;
 
-use Mcp\Schema\Request\GetPromptRequest;
-
 /**
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 final class PromptGetException extends \RuntimeException implements ExceptionInterface
 {
-    public function __construct(
-        public readonly GetPromptRequest $request,
-        ?\Throwable $previous = null,
-    ) {
-        parent::__construct(\sprintf('Handling prompt "%s" failed with error: "%s".', $request->name, $previous->getMessage()), previous: $previous);
-    }
 }
diff --git a/src/Exception/PromptNotFoundException.php b/src/Exception/PromptNotFoundException.php
index 82872e8b..81b7c6e5 100644
--- a/src/Exception/PromptNotFoundException.php
+++ b/src/Exception/PromptNotFoundException.php
@@ -11,16 +11,14 @@
 
 namespace Mcp\Exception;
 
-use Mcp\Schema\Request\GetPromptRequest;
-
 /**
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 final class PromptNotFoundException extends \RuntimeException implements NotFoundExceptionInterface
 {
     public function __construct(
-        public readonly GetPromptRequest $request,
+        public readonly string $name,
     ) {
-        parent::__construct(\sprintf('Prompt not found for name: "%s".', $request->name));
+        parent::__construct(\sprintf('Prompt not found: "%s".', $name));
     }
 }
diff --git a/src/Exception/ResourceNotFoundException.php b/src/Exception/ResourceNotFoundException.php
index b5624bbc..420ac1a8 100644
--- a/src/Exception/ResourceNotFoundException.php
+++ b/src/Exception/ResourceNotFoundException.php
@@ -11,16 +11,14 @@
 
 namespace Mcp\Exception;
 
-use Mcp\Schema\Request\ReadResourceRequest;
-
 /**
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 final class ResourceNotFoundException extends \RuntimeException implements NotFoundExceptionInterface
 {
     public function __construct(
-        public readonly ReadResourceRequest $request,
+        public readonly string $uri,
     ) {
-        parent::__construct(\sprintf('Resource not found for uri: "%s".', $request->uri));
+        parent::__construct(\sprintf('Resource not found for uri: "%s".', $uri));
     }
 }
diff --git a/src/Exception/ResourceReadException.php b/src/Exception/ResourceReadException.php
index 913064b2..a89dec8e 100644
--- a/src/Exception/ResourceReadException.php
+++ b/src/Exception/ResourceReadException.php
@@ -11,17 +11,9 @@
 
 namespace Mcp\Exception;
 
-use Mcp\Schema\Request\ReadResourceRequest;
-
 /**
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 final class ResourceReadException extends \RuntimeException implements ExceptionInterface
 {
-    public function __construct(
-        public readonly ReadResourceRequest $request,
-        ?\Throwable $previous = null,
-    ) {
-        parent::__construct(\sprintf('Reading resource "%s" failed with error: "%s".', $request->uri, $previous?->getMessage() ?? ''), previous: $previous);
-    }
 }
diff --git a/src/Exception/ToolCallException.php b/src/Exception/ToolCallException.php
index 71978d9d..01ba9f45 100644
--- a/src/Exception/ToolCallException.php
+++ b/src/Exception/ToolCallException.php
@@ -11,17 +11,9 @@
 
 namespace Mcp\Exception;
 
-use Mcp\Schema\Request\CallToolRequest;
-
 /**
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 final class ToolCallException extends \RuntimeException implements ExceptionInterface
 {
-    public function __construct(
-        public readonly CallToolRequest $request,
-        ?\Throwable $previous = null,
-    ) {
-        parent::__construct(\sprintf('Tool call "%s" failed with error: "%s".', $request->name, $previous?->getMessage() ?? ''), previous: $previous);
-    }
 }
diff --git a/src/Exception/ToolNotFoundException.php b/src/Exception/ToolNotFoundException.php
index 3795d74e..0a864e75 100644
--- a/src/Exception/ToolNotFoundException.php
+++ b/src/Exception/ToolNotFoundException.php
@@ -11,16 +11,14 @@
 
 namespace Mcp\Exception;
 
-use Mcp\Schema\Request\CallToolRequest;
-
 /**
  * @author Tobias Nyholm <tobias.nyholm@gmail.com>
  */
 final class ToolNotFoundException extends \RuntimeException implements NotFoundExceptionInterface
 {
     public function __construct(
-        public readonly CallToolRequest $request,
+        public readonly string $name,
     ) {
-        parent::__construct(\sprintf('Tool not found for call: "%s".', $request->name));
+        parent::__construct(\sprintf('Tool not found: "%s".', $name));
     }
 }
diff --git a/src/Schema/JsonRpc/Error.php b/src/Schema/JsonRpc/Error.php
index ae802580..d5273eb1 100644
--- a/src/Schema/JsonRpc/Error.php
+++ b/src/Schema/JsonRpc/Error.php
@@ -106,6 +106,11 @@ public static function forServerError(string $message, string|int $id = ''): sel
         return new self($id, self::SERVER_ERROR, $message);
     }
 
+    public static function forResourceNotFound(string $message, string|int $id = ''): self
+    {
+        return new self($id, self::RESOURCE_NOT_FOUND, $message);
+    }
+
     public function getId(): string|int
     {
         return $this->id;
diff --git a/src/Server/Handler/Request/CallToolHandler.php b/src/Server/Handler/Request/CallToolHandler.php
index 79413908..df4aff51 100644
--- a/src/Server/Handler/Request/CallToolHandler.php
+++ b/src/Server/Handler/Request/CallToolHandler.php
@@ -13,9 +13,9 @@
 
 use Mcp\Capability\Registry\ReferenceHandlerInterface;
 use Mcp\Capability\Registry\ReferenceProviderInterface;
-use Mcp\Exception\ExceptionInterface;
 use Mcp\Exception\ToolCallException;
 use Mcp\Exception\ToolNotFoundException;
+use Mcp\Schema\Content\TextContent;
 use Mcp\Schema\JsonRpc\Error;
 use Mcp\Schema\JsonRpc\Request;
 use Mcp\Schema\JsonRpc\Response;
@@ -59,9 +59,6 @@ public function handle(Request $request, SessionInterface $session): Response|Er
 
         try {
             $reference = $this->referenceProvider->getTool($toolName);
-            if (null === $reference) {
-                throw new ToolNotFoundException($request);
-            }
 
             $arguments['_session'] = $session;
 
@@ -77,17 +74,19 @@ public function handle(Request $request, SessionInterface $session): Response|Er
             ]);
 
             return new Response($request->getId(), $result);
-        } catch (ToolNotFoundException $e) {
-            $this->logger->error('Tool not found', ['name' => $toolName]);
-
-            return new Error($request->getId(), Error::METHOD_NOT_FOUND, $e->getMessage());
-        } catch (ToolCallException|ExceptionInterface $e) {
+        } catch (ToolCallException $e) {
             $this->logger->error(\sprintf('Error while executing tool "%s": "%s".', $toolName, $e->getMessage()), [
                 'tool' => $toolName,
                 'arguments' => $arguments,
             ]);
 
-            return Error::forInternalError('Error while executing tool', $request->getId());
+            $errorContent = [new TextContent($e->getMessage())];
+
+            return new Response($request->getId(), CallToolResult::error($errorContent));
+        } catch (ToolNotFoundException $e) {
+            $this->logger->error('Tool not found', ['name' => $toolName]);
+
+            return new Error($request->getId(), Error::METHOD_NOT_FOUND, $e->getMessage());
         } catch (\Throwable $e) {
             $this->logger->error('Unhandled error during tool execution', [
                 'name' => $toolName,
diff --git a/src/Server/Handler/Request/CompletionCompleteHandler.php b/src/Server/Handler/Request/CompletionCompleteHandler.php
index c3d9f844..f1c1b9d6 100644
--- a/src/Server/Handler/Request/CompletionCompleteHandler.php
+++ b/src/Server/Handler/Request/CompletionCompleteHandler.php
@@ -13,10 +13,14 @@
 
 use Mcp\Capability\Completion\ProviderInterface;
 use Mcp\Capability\Registry\ReferenceProviderInterface;
+use Mcp\Exception\PromptNotFoundException;
+use Mcp\Exception\ResourceNotFoundException;
 use Mcp\Schema\JsonRpc\Error;
 use Mcp\Schema\JsonRpc\Request;
 use Mcp\Schema\JsonRpc\Response;
+use Mcp\Schema\PromptReference;
 use Mcp\Schema\Request\CompletionCompleteRequest;
+use Mcp\Schema\ResourceReference;
 use Mcp\Schema\Result\CompletionCompleteResult;
 use Mcp\Server\Session\SessionInterface;
 use Psr\Container\ContainerInterface;
@@ -51,41 +55,38 @@ public function handle(Request $request, SessionInterface $session): Response|Er
         $name = $request->argument['name'] ?? '';
         $value = $request->argument['value'] ?? '';
 
-        $reference = match ($request->ref->type) {
-            'ref/prompt' => $this->referenceProvider->getPrompt($request->ref->name),
-            'ref/resource' => $this->referenceProvider->getResourceTemplate($request->ref->uri),
-            default => null,
-        };
-
-        if (null === $reference) {
-            return new Response($request->getId(), new CompletionCompleteResult([]));
-        }
+        try {
+            $reference = match (true) {
+                $request->ref instanceof PromptReference => $this->referenceProvider->getPrompt($request->ref->name),
+                $request->ref instanceof ResourceReference => $this->referenceProvider->getResource($request->ref->uri),
+            };
 
-        $providers = $reference->completionProviders;
-        $provider = $providers[$name] ?? null;
-        if (null === $provider) {
-            return new Response($request->getId(), new CompletionCompleteResult([]));
-        }
+            $providers = $reference->completionProviders;
+            $provider = $providers[$name] ?? null;
+            if (null === $provider) {
+                return new Response($request->getId(), new CompletionCompleteResult([]));
+            }
 
-        if (\is_string($provider)) {
-            if (!class_exists($provider)) {
-                return Error::forInternalError('Invalid completion provider', $request->getId());
+            if (\is_string($provider)) {
+                if (!class_exists($provider)) {
+                    return Error::forInternalError('Invalid completion provider', $request->getId());
+                }
+                $provider = $this->container?->has($provider) ? $this->container->get($provider) : new $provider();
             }
-            $provider = $this->container?->has($provider) ? $this->container->get($provider) : new $provider();
-        }
 
-        if (!$provider instanceof ProviderInterface) {
-            return Error::forInternalError('Invalid completion provider type', $request->getId());
-        }
+            if (!$provider instanceof ProviderInterface) {
+                return Error::forInternalError('Invalid completion provider type', $request->getId());
+            }
 
-        try {
             $completions = $provider->getCompletions($value);
             $total = \count($completions);
             $hasMore = $total > 100;
             $paged = \array_slice($completions, 0, 100);
 
             return new Response($request->getId(), new CompletionCompleteResult($paged, $total, $hasMore));
-        } catch (\Throwable) {
+        } catch (PromptNotFoundException|ResourceNotFoundException $e) {
+            return Error::forResourceNotFound($e->getMessage(), $request->getId());
+        } catch (\Throwable $e) {
             return Error::forInternalError('Error while handling completion request', $request->getId());
         }
     }
diff --git a/src/Server/Handler/Request/GetPromptHandler.php b/src/Server/Handler/Request/GetPromptHandler.php
index 28e5e909..1c8758ab 100644
--- a/src/Server/Handler/Request/GetPromptHandler.php
+++ b/src/Server/Handler/Request/GetPromptHandler.php
@@ -13,7 +13,6 @@
 
 use Mcp\Capability\Registry\ReferenceHandlerInterface;
 use Mcp\Capability\Registry\ReferenceProviderInterface;
-use Mcp\Exception\ExceptionInterface;
 use Mcp\Exception\PromptGetException;
 use Mcp\Exception\PromptNotFoundException;
 use Mcp\Schema\JsonRpc\Error;
@@ -56,9 +55,6 @@ public function handle(Request $request, SessionInterface $session): Response|Er
 
         try {
             $reference = $this->referenceProvider->getPrompt($promptName);
-            if (null === $reference) {
-                throw new PromptNotFoundException($request);
-            }
 
             $arguments['_session'] = $session;
 
@@ -67,18 +63,18 @@ public function handle(Request $request, SessionInterface $session): Response|Er
             $formatted = $reference->formatResult($result);
 
             return new Response($request->getId(), new GetPromptResult($formatted));
+        } catch (PromptGetException $e) {
+            $this->logger->error(\sprintf('Error while handling prompt "%s": "%s".', $promptName, $e->getMessage()));
+
+            return Error::forInternalError($e->getMessage(), $request->getId());
         } catch (PromptNotFoundException $e) {
             $this->logger->error('Prompt not found', ['prompt_name' => $promptName]);
 
-            return new Error($request->getId(), Error::METHOD_NOT_FOUND, $e->getMessage());
-        } catch (PromptGetException|ExceptionInterface $e) {
-            $this->logger->error('Error while handling prompt', ['prompt_name' => $promptName]);
-
-            return Error::forInternalError('Error while handling prompt: '.$e->getMessage(), $request->getId());
+            return Error::forResourceNotFound($e->getMessage(), $request->getId());
         } catch (\Throwable $e) {
-            $this->logger->error('Error while handling prompt', ['prompt_name' => $promptName]);
+            $this->logger->error(\sprintf('Unexpected error while handling prompt "%s": "%s".', $promptName, $e->getMessage()));
 
-            return Error::forInternalError('Error while handling prompt: '.$e->getMessage(), $request->getId());
+            return Error::forInternalError('Error while handling prompt', $request->getId());
         }
     }
 }
diff --git a/src/Server/Handler/Request/ReadResourceHandler.php b/src/Server/Handler/Request/ReadResourceHandler.php
index 19e426aa..c5160cd5 100644
--- a/src/Server/Handler/Request/ReadResourceHandler.php
+++ b/src/Server/Handler/Request/ReadResourceHandler.php
@@ -15,6 +15,7 @@
 use Mcp\Capability\Registry\ReferenceProviderInterface;
 use Mcp\Capability\Registry\ResourceTemplateReference;
 use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Exception\ResourceReadException;
 use Mcp\Schema\JsonRpc\Error;
 use Mcp\Schema\JsonRpc\Request;
 use Mcp\Schema\JsonRpc\Response;
@@ -56,9 +57,6 @@ public function handle(Request $request, SessionInterface $session): Response|Er
 
         try {
             $reference = $this->referenceProvider->getResource($uri);
-            if (null === $reference) {
-                throw new ResourceNotFoundException($request);
-            }
 
             $arguments = [
                 'uri' => $uri,
@@ -77,12 +75,16 @@ public function handle(Request $request, SessionInterface $session): Response|Er
             }
 
             return new Response($request->getId(), new ReadResourceResult($formatted));
+        } catch (ResourceReadException $e) {
+            $this->logger->error(\sprintf('Error while reading resource "%s": "%s".', $uri, $e->getMessage()));
+
+            return Error::forInternalError($e->getMessage(), $request->getId());
         } catch (ResourceNotFoundException $e) {
             $this->logger->error('Resource not found', ['uri' => $uri]);
 
-            return new Error($request->getId(), Error::RESOURCE_NOT_FOUND, $e->getMessage());
+            return Error::forResourceNotFound($e->getMessage(), $request->getId());
         } catch (\Throwable $e) {
-            $this->logger->error(\sprintf('Error while reading resource "%s": "%s".', $uri, $e->getMessage()));
+            $this->logger->error(\sprintf('Unexpected error while reading resource "%s": "%s".', $uri, $e->getMessage()));
 
             return Error::forInternalError('Error while reading resource', $request->getId());
         }
diff --git a/tests/Unit/Capability/Registry/RegistryProviderTest.php b/tests/Unit/Capability/Registry/RegistryProviderTest.php
index b1eaa857..cebf474c 100644
--- a/tests/Unit/Capability/Registry/RegistryProviderTest.php
+++ b/tests/Unit/Capability/Registry/RegistryProviderTest.php
@@ -16,6 +16,9 @@
 use Mcp\Capability\Registry\ResourceReference;
 use Mcp\Capability\Registry\ResourceTemplateReference;
 use Mcp\Capability\Registry\ToolReference;
+use Mcp\Exception\PromptNotFoundException;
+use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Exception\ToolNotFoundException;
 use Mcp\Schema\Prompt;
 use Mcp\Schema\Resource;
 use Mcp\Schema\ResourceTemplate;
@@ -45,10 +48,12 @@ public function testGetToolReturnsRegisteredTool(): void
         $this->assertFalse($toolRef->isManual);
     }
 
-    public function testGetToolReturnsNullForUnregisteredTool(): void
+    public function testGetToolThrowsExceptionForUnregisteredTool(): void
     {
-        $toolRef = $this->registry->getTool('non_existent_tool');
-        $this->assertNull($toolRef);
+        $this->expectException(ToolNotFoundException::class);
+        $this->expectExceptionMessage('Tool not found: "non_existent_tool".');
+
+        $this->registry->getTool('non_existent_tool');
     }
 
     public function testGetResourceReturnsRegisteredResource(): void
@@ -65,10 +70,12 @@ public function testGetResourceReturnsRegisteredResource(): void
         $this->assertFalse($resourceRef->isManual);
     }
 
-    public function testGetResourceReturnsNullForUnregisteredResource(): void
+    public function testGetResourceThrowsExceptionForUnregisteredResource(): void
     {
-        $resourceRef = $this->registry->getResource('test://non_existent');
-        $this->assertNull($resourceRef);
+        $this->expectException(ResourceNotFoundException::class);
+        $this->expectExceptionMessage('Resource not found for uri: "test://non_existent".');
+
+        $this->registry->getResource('test://non_existent');
     }
 
     public function testGetResourceMatchesResourceTemplate(): void
@@ -84,15 +91,17 @@ public function testGetResourceMatchesResourceTemplate(): void
         $this->assertEquals($handler, $resourceRef->handler);
     }
 
-    public function testGetResourceWithIncludeTemplatesFalse(): void
+    public function testGetResourceWithIncludeTemplatesFalseThrowsException(): void
     {
         $template = $this->createValidResourceTemplate('test://{id}');
         $handler = fn (string $id) => "content for {$id}";
 
         $this->registry->registerResourceTemplate($template, $handler);
 
-        $resourceRef = $this->registry->getResource('test://123', false);
-        $this->assertNull($resourceRef);
+        $this->expectException(ResourceNotFoundException::class);
+        $this->expectExceptionMessage('Resource not found for uri: "test://123".');
+
+        $this->registry->getResource('test://123', false);
     }
 
     public function testGetResourcePrefersDirectResourceOverTemplate(): void
@@ -125,10 +134,12 @@ public function testGetResourceTemplateReturnsRegisteredTemplate(): void
         $this->assertFalse($templateRef->isManual);
     }
 
-    public function testGetResourceTemplateReturnsNullForUnregisteredTemplate(): void
+    public function testGetResourceTemplateThrowsExceptionForUnregisteredTemplate(): void
     {
-        $templateRef = $this->registry->getResourceTemplate('test://{non_existent}');
-        $this->assertNull($templateRef);
+        $this->expectException(ResourceNotFoundException::class);
+        $this->expectExceptionMessage('Resource not found for uri: "test://{non_existent}".');
+
+        $this->registry->getResourceTemplate('test://{non_existent}');
     }
 
     public function testGetPromptReturnsRegisteredPrompt(): void
@@ -145,10 +156,12 @@ public function testGetPromptReturnsRegisteredPrompt(): void
         $this->assertFalse($promptRef->isManual);
     }
 
-    public function testGetPromptReturnsNullForUnregisteredPrompt(): void
+    public function testGetPromptThrowsExceptionForUnregisteredPrompt(): void
     {
-        $promptRef = $this->registry->getPrompt('non_existent_prompt');
-        $this->assertNull($promptRef);
+        $this->expectException(PromptNotFoundException::class);
+        $this->expectExceptionMessage('Prompt not found: "non_existent_prompt".');
+
+        $this->registry->getPrompt('non_existent_prompt');
     }
 
     public function testGetToolsReturnsAllRegisteredTools(): void
diff --git a/tests/Unit/Capability/Registry/RegistryTest.php b/tests/Unit/Capability/Registry/RegistryTest.php
index e1f47689..33cb967e 100644
--- a/tests/Unit/Capability/Registry/RegistryTest.php
+++ b/tests/Unit/Capability/Registry/RegistryTest.php
@@ -13,6 +13,9 @@
 
 use Mcp\Capability\Completion\EnumCompletionProvider;
 use Mcp\Capability\Registry;
+use Mcp\Exception\PromptNotFoundException;
+use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Exception\ToolNotFoundException;
 use Mcp\Schema\Prompt;
 use Mcp\Schema\Resource;
 use Mcp\Schema\ResourceTemplate;
@@ -264,23 +267,36 @@ public function testClearRemovesOnlyDiscoveredElements(): void
         $this->registry->registerResourceTemplate($manualTemplate, fn () => 'manual', [], true);
         $this->registry->registerResourceTemplate($discoveredTemplate, fn () => 'discovered', [], false);
 
-        $this->logger
-            ->expects($this->once())
-            ->method('debug')
-            ->with('Removed 4 discovered elements from internal registry.');
+        // Test that all elements exist
+        $this->registry->getTool('manual_tool');
+        $this->registry->getResource('test://manual');
+        $this->registry->getPrompt('manual_prompt');
+        $this->registry->getResourceTemplate('manual://{id}');
+        $this->registry->getTool('discovered_tool');
+        $this->registry->getResource('test://discovered');
+        $this->registry->getPrompt('discovered_prompt');
+        $this->registry->getResourceTemplate('discovered://{id}');
 
         $this->registry->clear();
 
-        $this->assertNotNull($this->registry->getTool('manual_tool'));
-        $this->assertNull($this->registry->getTool('discovered_tool'));
-        $this->assertNotNull($this->registry->getResource('test://manual'));
-        $this->assertNull(
-            $this->registry->getResource('test://discovered', false),
-        ); // Don't include templates to avoid debug log
-        $this->assertNotNull($this->registry->getPrompt('manual_prompt'));
-        $this->assertNull($this->registry->getPrompt('discovered_prompt'));
-        $this->assertNotNull($this->registry->getResourceTemplate('manual://{id}'));
-        $this->assertNull($this->registry->getResourceTemplate('discovered://{id}'));
+        // Manual elements should still exist
+        $this->registry->getTool('manual_tool');
+        $this->registry->getResource('test://manual');
+        $this->registry->getPrompt('manual_prompt');
+        $this->registry->getResourceTemplate('manual://{id}');
+
+        // Test that all discovered elements throw exceptions
+        $this->expectException(ToolNotFoundException::class);
+        $this->registry->getTool('discovered_tool');
+
+        $this->expectException(ResourceNotFoundException::class);
+        $this->registry->getResource('test://discovered');
+
+        $this->expectException(PromptNotFoundException::class);
+        $this->registry->getPrompt('discovered_prompt');
+
+        $this->expectException(ResourceNotFoundException::class);
+        $this->registry->getResourceTemplate('discovered://{id}');
     }
 
     public function testClearLogsNothingWhenNoDiscoveredElements(): void
@@ -294,7 +310,7 @@ public function testClearLogsNothingWhenNoDiscoveredElements(): void
 
         $this->registry->clear();
 
-        $this->assertNotNull($this->registry->getTool('manual_tool'));
+        $this->registry->getTool('manual_tool');
     }
 
     public function testRegisterToolHandlesStringHandler(): void
diff --git a/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php b/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php
index 359afa1b..00b410f2 100644
--- a/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php
+++ b/tests/Unit/Server/Handler/Request/CallToolHandlerTest.php
@@ -164,7 +164,7 @@ public function testHandleToolNotFoundExceptionReturnsError(): void
             ->expects($this->once())
             ->method('getTool')
             ->with('nonexistent_tool')
-            ->willThrowException(new ToolNotFoundException($request));
+            ->willThrowException(new ToolNotFoundException('nonexistent_tool'));
 
         $this->logger
             ->expects($this->once())
@@ -177,10 +177,10 @@ public function testHandleToolNotFoundExceptionReturnsError(): void
         $this->assertEquals(Error::METHOD_NOT_FOUND, $response->code);
     }
 
-    public function testHandleToolExecutionExceptionReturnsError(): void
+    public function testHandleToolCallExceptionReturnsResponseWithErrorResult(): void
     {
         $request = $this->createCallToolRequest('failing_tool', ['param' => 'value']);
-        $exception = new ToolCallException($request, new \RuntimeException('Tool execution failed'));
+        $exception = new ToolCallException('Tool execution failed');
 
         $toolReference = $this->createMock(ToolReference::class);
         $this->referenceProvider
@@ -201,9 +201,15 @@ public function testHandleToolExecutionExceptionReturnsError(): void
 
         $response = $this->handler->handle($request, $this->session);
 
-        $this->assertInstanceOf(Error::class, $response);
+        $this->assertInstanceOf(Response::class, $response);
         $this->assertEquals($request->getId(), $response->id);
-        $this->assertEquals(Error::INTERNAL_ERROR, $response->code);
+
+        $result = $response->result;
+        $this->assertInstanceOf(CallToolResult::class, $result);
+        $this->assertTrue($result->isError);
+        $this->assertCount(1, $result->content);
+        $this->assertInstanceOf(TextContent::class, $result->content[0]);
+        $this->assertEquals('Tool execution failed', $result->content[0]->text);
     }
 
     public function testHandleWithNullResult(): void
@@ -246,7 +252,7 @@ public function testConstructorWithDefaultLogger(): void
     public function testHandleLogsErrorWithCorrectParameters(): void
     {
         $request = $this->createCallToolRequest('test_tool', ['key1' => 'value1', 'key2' => 42]);
-        $exception = new ToolCallException($request, new \RuntimeException('Custom error message'));
+        $exception = new ToolCallException('Custom error message');
 
         $toolReference = $this->createMock(ToolReference::class);
         $this->referenceProvider
@@ -265,7 +271,7 @@ public function testHandleLogsErrorWithCorrectParameters(): void
             ->expects($this->once())
             ->method('error')
             ->with(
-                'Error while executing tool "test_tool": "Tool call "test_tool" failed with error: "Custom error message".".',
+                'Error while executing tool "test_tool": "Custom error message".',
                 [
                     'tool' => 'test_tool',
                     'arguments' => ['key1' => 'value1', 'key2' => 42, '_session' => $this->session],
@@ -274,8 +280,43 @@ public function testHandleLogsErrorWithCorrectParameters(): void
 
         $response = $this->handler->handle($request, $this->session);
 
+        // ToolCallException should now return Response with CallToolResult having isError=true
+        $this->assertInstanceOf(Response::class, $response);
+        $this->assertEquals($request->getId(), $response->id);
+
+        $result = $response->result;
+        $this->assertInstanceOf(CallToolResult::class, $result);
+        $this->assertTrue($result->isError);
+        $this->assertCount(1, $result->content);
+        $this->assertInstanceOf(TextContent::class, $result->content[0]);
+        $this->assertEquals('Custom error message', $result->content[0]->text);
+    }
+
+    public function testHandleGenericExceptionReturnsError(): void
+    {
+        $request = $this->createCallToolRequest('failing_tool', ['param' => 'value']);
+        $exception = new \RuntimeException('Internal database connection failed');
+
+        $toolReference = $this->createMock(ToolReference::class);
+        $this->referenceProvider
+            ->expects($this->once())
+            ->method('getTool')
+            ->with('failing_tool')
+            ->willReturn($toolReference);
+
+        $this->referenceHandler
+            ->expects($this->once())
+            ->method('handle')
+            ->with($toolReference, ['param' => 'value', '_session' => $this->session])
+            ->willThrowException($exception);
+
+        $response = $this->handler->handle($request, $this->session);
+
+        // Generic exceptions should return Error, not Response
         $this->assertInstanceOf(Error::class, $response);
+        $this->assertEquals($request->getId(), $response->id);
         $this->assertEquals(Error::INTERNAL_ERROR, $response->code);
+        $this->assertEquals('Error while executing tool', $response->message);
     }
 
     public function testHandleWithSpecialCharactersInToolName(): void
diff --git a/tests/Unit/Server/Handler/Request/GetPromptHandlerTest.php b/tests/Unit/Server/Handler/Request/GetPromptHandlerTest.php
index b7f5d259..03abe085 100644
--- a/tests/Unit/Server/Handler/Request/GetPromptHandlerTest.php
+++ b/tests/Unit/Server/Handler/Request/GetPromptHandlerTest.php
@@ -231,7 +231,7 @@ public function testHandlePromptGetWithMultipleMessages(): void
     public function testHandlePromptNotFoundExceptionReturnsError(): void
     {
         $request = $this->createGetPromptRequest('nonexistent_prompt');
-        $exception = new PromptNotFoundException($request);
+        $exception = new PromptNotFoundException('nonexistent_prompt');
 
         $this->referenceProvider
             ->expects($this->once())
@@ -243,14 +243,14 @@ public function testHandlePromptNotFoundExceptionReturnsError(): void
 
         $this->assertInstanceOf(Error::class, $response);
         $this->assertEquals($request->getId(), $response->id);
-        $this->assertEquals(Error::METHOD_NOT_FOUND, $response->code);
-        $this->assertEquals('Prompt not found for name: "nonexistent_prompt".', $response->message);
+        $this->assertEquals(Error::RESOURCE_NOT_FOUND, $response->code);
+        $this->assertEquals('Prompt not found: "nonexistent_prompt".', $response->message);
     }
 
     public function testHandlePromptGetExceptionReturnsError(): void
     {
         $request = $this->createGetPromptRequest('failing_prompt');
-        $exception = new PromptGetException($request, new \RuntimeException('Failed to get prompt'));
+        $exception = new PromptGetException('Failed to get prompt');
 
         $this->referenceProvider
             ->expects($this->once())
@@ -263,7 +263,7 @@ public function testHandlePromptGetExceptionReturnsError(): void
         $this->assertInstanceOf(Error::class, $response);
         $this->assertEquals($request->getId(), $response->id);
         $this->assertEquals(Error::INTERNAL_ERROR, $response->code);
-        $this->assertEquals('Error while handling prompt: Handling prompt "failing_prompt" failed with error: "Failed to get prompt".', $response->message);
+        $this->assertEquals('Failed to get prompt', $response->message);
     }
 
     public function testHandlePromptGetWithComplexArguments(): void
diff --git a/tests/Unit/Server/Handler/Request/ReadResourceHandlerTest.php b/tests/Unit/Server/Handler/Request/ReadResourceHandlerTest.php
index 2c54110d..92b5a6f2 100644
--- a/tests/Unit/Server/Handler/Request/ReadResourceHandlerTest.php
+++ b/tests/Unit/Server/Handler/Request/ReadResourceHandlerTest.php
@@ -178,7 +178,7 @@ public function testHandleResourceNotFoundExceptionReturnsSpecificError(): void
     {
         $uri = 'file://nonexistent/file.txt';
         $request = $this->createReadResourceRequest($uri);
-        $exception = new ResourceNotFoundException($request);
+        $exception = new ResourceNotFoundException($uri);
 
         $this->referenceProvider
             ->expects($this->once())
@@ -194,14 +194,31 @@ public function testHandleResourceNotFoundExceptionReturnsSpecificError(): void
         $this->assertEquals('Resource not found for uri: "'.$uri.'".', $response->message);
     }
 
-    public function testHandleResourceReadExceptionReturnsGenericError(): void
+    public function testHandleResourceReadExceptionReturnsActualErrorMessage(): void
     {
         $uri = 'file://corrupted/file.txt';
         $request = $this->createReadResourceRequest($uri);
-        $exception = new ResourceReadException(
-            $request,
-            new \RuntimeException('Failed to read resource: corrupted data'),
-        );
+        $exception = new ResourceReadException('Failed to read resource: corrupted data');
+
+        $this->referenceProvider
+            ->expects($this->once())
+            ->method('getResource')
+            ->with($uri)
+            ->willThrowException($exception);
+
+        $response = $this->handler->handle($request, $this->session);
+
+        $this->assertInstanceOf(Error::class, $response);
+        $this->assertEquals($request->getId(), $response->id);
+        $this->assertEquals(Error::INTERNAL_ERROR, $response->code);
+        $this->assertEquals('Failed to read resource: corrupted data', $response->message);
+    }
+
+    public function testHandleGenericExceptionReturnsGenericError(): void
+    {
+        $uri = 'file://problematic/file.txt';
+        $request = $this->createReadResourceRequest($uri);
+        $exception = new \RuntimeException('Internal database connection failed');
 
         $this->referenceProvider
             ->expects($this->once())
@@ -382,7 +399,7 @@ public function testHandleResourceNotFoundWithCustomMessage(): void
     {
         $uri = 'file://custom/missing.txt';
         $request = $this->createReadResourceRequest($uri);
-        $exception = new ResourceNotFoundException($request);
+        $exception = new ResourceNotFoundException($uri);
 
         $this->referenceProvider
             ->expects($this->once())