mcp: update to jsonschema that does not validate structs

docs/server.md

@@ -364,9 +364,9 @@ the `Tool.InputSchema` explicitly:
 
 ```go
 // Distinguished Go types allow custom schemas to be reused during inference.
-customSchemas := map[any]*jsonschema.Schema{
-	Probability(0):  {Type: "number", Minimum: jsonschema.Ptr(0.0), Maximum: jsonschema.Ptr(1.0)},
-	WeatherType(""): {Type: "string", Enum: []any{Sunny, PartlyCloudy, Cloudy, Rainy, Snowy}},
+customSchemas := map[reflect.Type]*jsonschema.Schema{
+	reflect.TypeFor[Probability](): {Type: "number", Minimum: jsonschema.Ptr(0.0), Maximum: jsonschema.Ptr(1.0)},
+	reflect.TypeFor[WeatherType](): {Type: "string", Enum: []any{Sunny, PartlyCloudy, Cloudy, Rainy, Snowy}},
 }
 opts := &jsonschema.ForOptions{TypeSchemas: customSchemas}
 in, err := jsonschema.For[WeatherInput](opts)

examples/server/auth-middleware/go.mod

@@ -8,7 +8,7 @@ require (
 )
 
 require (
-	github.com/google/jsonschema-go v0.2.3 // indirect
+	github.com/google/jsonschema-go v0.3.0 // indirect
 	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 )
 

examples/server/auth-middleware/go.sum

@@ -2,8 +2,8 @@ github.com/golang-jwt/jwt/v5 v5.2.2 h1:Rl4B7itRWVtYIHFrSNd7vhTiz9UpLdi6gZhZ3wEeD
 github.com/golang-jwt/jwt/v5 v5.2.2/go.mod h1:pqrtFR0X4osieyHYxtmOUWsAWrfe1Q5UVIyoH402zdk=
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
-github.com/google/jsonschema-go v0.2.3 h1:dkP3B96OtZKKFvdrUSaDkL+YDx8Uw9uC4Y+eukpCnmM=
-github.com/google/jsonschema-go v0.2.3/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
+github.com/google/jsonschema-go v0.3.0 h1:6AH2TxVNtk3IlvkkhjrtbUc4S8AvO0Xii0DxIygDg+Q=
+github.com/google/jsonschema-go v0.3.0/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
 github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
 github.com/yosida95/uritemplate/v3 v3.0.2/go.mod h1:ILOh0sOhIJR3+L/8afwt/kE++YT040gmv5BQTMR2HP4=
 golang.org/x/tools v0.34.0 h1:qIpSLOxeCYGg9TrcJokLBG4KFA6d795g0xkBkiESGlo=

examples/server/rate-limiting/go.mod

@@ -8,7 +8,7 @@ require (
 )
 
 require (
-	github.com/google/jsonschema-go v0.2.3 // indirect
+	github.com/google/jsonschema-go v0.3.0 // indirect
 	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 )
 

examples/server/rate-limiting/go.sum

@@ -1,7 +1,7 @@
 github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
-github.com/google/jsonschema-go v0.2.3 h1:dkP3B96OtZKKFvdrUSaDkL+YDx8Uw9uC4Y+eukpCnmM=
-github.com/google/jsonschema-go v0.2.3/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
+github.com/google/jsonschema-go v0.3.0 h1:6AH2TxVNtk3IlvkkhjrtbUc4S8AvO0Xii0DxIygDg+Q=
+github.com/google/jsonschema-go v0.3.0/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
 github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
 github.com/yosida95/uritemplate/v3 v3.0.2/go.mod h1:ILOh0sOhIJR3+L/8afwt/kE++YT040gmv5BQTMR2HP4=
 golang.org/x/time v0.12.0 h1:ScB/8o8olJvc+CQPWrK3fPZNfh7qgwCrY0zJmoEQLSE=

examples/server/toolschemas/main.go

@@ -54,27 +54,72 @@ func (t *manualGreeter) greet(_ context.Context, req *mcp.CallToolRequest) (*mcp
 	// Handle the parsing and validation of input and output.
 	//
 	// Note that errors here are treated as tool errors, not protocol errors.
+
+	// First, unmarshal to a map[string]any and validate.
+	if err := unmarshalAndValidate(req.Params.Arguments, t.inputSchema); err != nil {
+		return errf("invalid input: %v", err), nil
+	}
+
+	// Now unmarshal again to input.
 	var input Input
 	if err := json.Unmarshal(req.Params.Arguments, &input); err != nil {
 		return errf("failed to unmarshal arguments: %v", err), nil
 	}
-	if err := t.inputSchema.Validate(input); err != nil {
-		return errf("invalid input: %v", err), nil
-	}
 	output := Output{Greeting: "Hi " + input.Name}
-	if err := t.outputSchema.Validate(output); err != nil {
-		return errf("tool produced invalid output: %v", err), nil
-	}
 	outputJSON, err := json.Marshal(output)
 	if err != nil {
 		return errf("output failed to marshal: %v", err), nil
 	}
+	//
+	if err := unmarshalAndValidate(outputJSON, t.outputSchema); err != nil {
+		return errf("invalid output: %v", err), nil
+	}
+
 	return &mcp.CallToolResult{
 		Content:           []mcp.Content{&mcp.TextContent{Text: string(outputJSON)}},
 		StructuredContent: output,
 	}, nil
 }
 
+// unmarshalAndValidate unmarshals data to a map[string]any, then validates that against res.
+func unmarshalAndValidate(data []byte, res *jsonschema.Resolved) error {
+	var m map[string]any
+	if err := json.Unmarshal(data, &m); err != nil {
+		return err
+	}
+	return res.Validate(m)
+}
+
+var (
+	inputSchema = &jsonschema.Schema{
+		Type: "object",
+		Properties: map[string]*jsonschema.Schema{
+			"name": {Type: "string", MaxLength: jsonschema.Ptr(10)},
+		},
+	}
+	outputSchema = &jsonschema.Schema{
+		Type: "object",
+		Properties: map[string]*jsonschema.Schema{
+			"greeting": {Type: "string"},
+		},
+	}
+)
+
+func newManualGreeter() (*manualGreeter, error) {
+	resIn, err := inputSchema.Resolve(nil)
+	if err != nil {
+		return nil, err
+	}
+	resOut, err := outputSchema.Resolve(nil)
+	if err != nil {
+		return nil, err
+	}
+	return &manualGreeter{
+		inputSchema:  resIn,
+		outputSchema: resOut,
+	}, nil
+}
+
 func main() {
 	server := mcp.NewServer(&mcp.Implementation{Name: "greeter"}, nil)
 
@@ -90,27 +135,7 @@ func main() {
 	//
 	// We don't need to do all this work: below, we use jsonschema.For to start
 	// from the default schema.
-	var (
-		manual manualGreeter
-		err    error
-	)
-	inputSchema := &jsonschema.Schema{
-		Type: "object",
-		Properties: map[string]*jsonschema.Schema{
-			"name": {Type: "string", MaxLength: jsonschema.Ptr(10)},
-		},
-	}
-	manual.inputSchema, err = inputSchema.Resolve(nil)
-	if err != nil {
-		log.Fatal(err)
-	}
-	outputSchema := &jsonschema.Schema{
-		Type: "object",
-		Properties: map[string]*jsonschema.Schema{
-			"greeting": {Type: "string"},
-		},
-	}
-	manual.outputSchema, err = outputSchema.Resolve(nil)
+	manual, err := newManualGreeter()
 	if err != nil {
 		log.Fatal(err)
 	}

examples/server/toolschemas/main_test.go

@@ -0,0 +1,31 @@
+// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+
+	"github.com/modelcontextprotocol/go-sdk/mcp"
+)
+
+func TestGreet(t *testing.T) {
+	manual, err := newManualGreeter()
+	if err != nil {
+		t.Fatal(err)
+	}
+	res, err := manual.greet(context.Background(), &mcp.CallToolRequest{
+		Params: &mcp.CallToolParamsRaw{
+			Arguments: json.RawMessage(`{"name": "Bob"}`),
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.IsError {
+		t.Fatalf("tool error: %q", res.Content[0].(*mcp.TextContent).Text)
+	}
+}

go.mod

@@ -5,7 +5,7 @@ go 1.23.0
 require (
 	github.com/golang-jwt/jwt/v5 v5.2.2
 	github.com/google/go-cmp v0.7.0
-	github.com/google/jsonschema-go v0.2.3
+	github.com/google/jsonschema-go v0.3.0
 	github.com/yosida95/uritemplate/v3 v3.0.2
 	golang.org/x/tools v0.34.0
 )

go.sum

@@ -4,6 +4,10 @@ github.com/google/go-cmp v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
 github.com/google/go-cmp v0.7.0/go.mod h1:pXiqmnSA92OHEEa9HXL2W4E7lf9JzCmGVUdgjX3N/iU=
 github.com/google/jsonschema-go v0.2.3 h1:dkP3B96OtZKKFvdrUSaDkL+YDx8Uw9uC4Y+eukpCnmM=
 github.com/google/jsonschema-go v0.2.3/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
+github.com/google/jsonschema-go v0.2.4-0.20250922144851-e08864c65371 h1:e1VCqWtKpTYBOBhPcgGV5whTlMFpTbH5Ghm56wpxBsk=
+github.com/google/jsonschema-go v0.2.4-0.20250922144851-e08864c65371/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
+github.com/google/jsonschema-go v0.3.0 h1:6AH2TxVNtk3IlvkkhjrtbUc4S8AvO0Xii0DxIygDg+Q=
+github.com/google/jsonschema-go v0.3.0/go.mod h1:r5quNTdLOYEz95Ru18zA0ydNbBuYoo9tgaYcxEYhJVE=
 github.com/yosida95/uritemplate/v3 v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
 github.com/yosida95/uritemplate/v3 v3.0.2/go.mod h1:ILOh0sOhIJR3+L/8afwt/kE++YT040gmv5BQTMR2HP4=
 golang.org/x/tools v0.34.0 h1:qIpSLOxeCYGg9TrcJokLBG4KFA6d795g0xkBkiESGlo=

mcp/streamable_bench_test.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"net/http"
 	"net/http/httptest"
+	"reflect"
 	"testing"
 
 	"github.com/google/jsonschema-go/jsonschema"
@@ -17,9 +18,9 @@ import (
 func BenchmarkStreamableServing(b *testing.B) {
 	// This benchmark measures how fast we can handle a single tool on a
 	// streamable server, including tool validation and stream management.
-	customSchemas := map[any]*jsonschema.Schema{
-		Probability(0):  {Type: "number", Minimum: jsonschema.Ptr(0.0), Maximum: jsonschema.Ptr(1.0)},
-		WeatherType(""): {Type: "string", Enum: []any{Sunny, PartlyCloudy, Cloudy, Rainy, Snowy}},
+	customSchemas := map[reflect.Type]*jsonschema.Schema{
+		reflect.TypeFor[Probability](): {Type: "number", Minimum: jsonschema.Ptr(0.0), Maximum: jsonschema.Ptr(1.0)},
+		reflect.TypeFor[WeatherType](): {Type: "string", Enum: []any{Sunny, PartlyCloudy, Cloudy, Rainy, Snowy}},
 	}
 	opts := &jsonschema.ForOptions{TypeSchemas: customSchemas}
 	in, err := jsonschema.For[WeatherInput](opts)

mcp/tool_example_test.go

@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"log"
+	"reflect"
 	"time"
 
 	"github.com/google/jsonschema-go/jsonschema"
@@ -34,8 +35,8 @@ func ExampleAddTool_customMarshalling() {
 	// In this case, you can use jsonschema.For along with jsonschema.ForOptions
 	// to customize the schema inference for your custom type.
 	inputSchema, err := jsonschema.For[Input](&jsonschema.ForOptions{
-		TypeSchemas: map[any]*jsonschema.Schema{
-			MyDate{}: {Type: "string"},
+		TypeSchemas: map[reflect.Type]*jsonschema.Schema{
+			reflect.TypeFor[MyDate](): {Type: "string"},
 		},
 	})
 	if err != nil {
@@ -152,9 +153,9 @@ func ExampleAddTool_complexSchema() {
 	// !+customschemas
 
 	// Distinguished Go types allow custom schemas to be reused during inference.
-	customSchemas := map[any]*jsonschema.Schema{
-		Probability(0):  {Type: "number", Minimum: jsonschema.Ptr(0.0), Maximum: jsonschema.Ptr(1.0)},
-		WeatherType(""): {Type: "string", Enum: []any{Sunny, PartlyCloudy, Cloudy, Rainy, Snowy}},
+	customSchemas := map[reflect.Type]*jsonschema.Schema{
+		reflect.TypeFor[Probability](): {Type: "number", Minimum: jsonschema.Ptr(0.0), Maximum: jsonschema.Ptr(1.0)},
+		reflect.TypeFor[WeatherType](): {Type: "string", Enum: []any{Sunny, PartlyCloudy, Cloudy, Rainy, Snowy}},
 	}
 	opts := &jsonschema.ForOptions{TypeSchemas: customSchemas}
 	in, err := jsonschema.For[WeatherInput](opts)