diff --git a/src/strands/telemetry/tracer.py b/src/strands/telemetry/tracer.py
index a68aad8b7..c47a10c3f 100644
--- a/src/strands/telemetry/tracer.py
+++ b/src/strands/telemetry/tracer.py
@@ -80,10 +80,6 @@ class Tracer:
     When the OTEL_EXPORTER_OTLP_ENDPOINT environment variable is set, traces
     are sent to the OTLP endpoint.
 
-    Attributes:
-        use_latest_genai_conventions: If True, uses the latest experimental GenAI semantic conventions.
-        include_tool_definitions: If True, includes detailed tool definitions in the agent trace span.
-
     Both attributes are controlled by including "gen_ai_latest_experimental" or "gen_ai_tool_definitions",
     respectively, in the OTEL_SEMCONV_STABILITY_OPT_IN environment variable.
     """
@@ -98,8 +94,9 @@ def __init__(self) -> None:
 
         # Read OTEL_SEMCONV_STABILITY_OPT_IN environment variable
         opt_in_values = self._parse_semconv_opt_in()
+        ## To-do: should not set below attributes directly, use env var instead
         self.use_latest_genai_conventions = "gen_ai_latest_experimental" in opt_in_values
-        self.include_tool_definitions = "gen_ai_tool_definitions" in opt_in_values
+        self._include_tool_definitions = "gen_ai_tool_definitions" in opt_in_values
 
     def _parse_semconv_opt_in(self) -> set[str]:
         """Parse the OTEL_SEMCONV_STABILITY_OPT_IN environment variable.
@@ -587,7 +584,7 @@ def start_agent_span(
         if tools:
             attributes["gen_ai.agent.tools"] = serialize(tools)
 
-        if self.include_tool_definitions and tools_config:
+        if self._include_tool_definitions and tools_config:
             try:
                 tool_definitions = self._construct_tool_definitions(tools_config)
                 attributes["gen_ai.tool.definitions"] = serialize(tool_definitions)
diff --git a/tests/strands/telemetry/test_tracer.py b/tests/strands/telemetry/test_tracer.py
index 25d477588..98cfb459f 100644
--- a/tests/strands/telemetry/test_tracer.py
+++ b/tests/strands/telemetry/test_tracer.py
@@ -163,11 +163,11 @@ def test_start_model_invoke_span(mock_tracer):
         assert span is not None
 
 
-def test_start_model_invoke_span_latest_conventions(mock_tracer):
+def test_start_model_invoke_span_latest_conventions(mock_tracer, monkeypatch):
     """Test starting a model invoke span with the latest semantic conventions."""
     with mock.patch("strands.telemetry.tracer.trace_api.get_tracer", return_value=mock_tracer):
+        monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
         tracer = Tracer()
-        tracer.use_latest_genai_conventions = True
         tracer.tracer = mock_tracer
 
         mock_span = mock.MagicMock()
@@ -244,11 +244,11 @@ def test_end_model_invoke_span(mock_span):
     mock_span.end.assert_called_once()
 
 
-def test_end_model_invoke_span_latest_conventions(mock_span):
+def test_end_model_invoke_span_latest_conventions(mock_span, monkeypatch):
     """Test ending a model invoke span with the latest semantic conventions."""
     with mock.patch("strands.telemetry.tracer.trace_api.get_tracer", return_value=mock_tracer):
+        monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
         tracer = Tracer()
-        tracer.use_latest_genai_conventions = True
         message = {"role": "assistant", "content": [{"text": "Response"}]}
         usage = Usage(inputTokens=10, outputTokens=20, totalTokens=30)
         metrics = Metrics(latencyMs=20, timeToFirstByteMs=10)
@@ -307,11 +307,11 @@ def test_start_tool_call_span(mock_tracer):
         assert span is not None
 
 
-def test_start_tool_call_span_latest_conventions(mock_tracer):
+def test_start_tool_call_span_latest_conventions(mock_tracer, monkeypatch):
     """Test starting a tool call span with the latest semantic conventions."""
     with mock.patch("strands.telemetry.tracer.trace_api.get_tracer", return_value=mock_tracer):
+        monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
         tracer = Tracer()
-        tracer.use_latest_genai_conventions = True
         tracer.tracer = mock_tracer
 
         mock_span = mock.MagicMock()
@@ -396,11 +396,11 @@ def test_start_swarm_span_with_contentblock_task(mock_tracer):
         assert span is not None
 
 
-def test_start_swarm_span_with_contentblock_task_latest_conventions(mock_tracer):
+def test_start_swarm_span_with_contentblock_task_latest_conventions(mock_tracer, monkeypatch):
     """Test starting a swarm call span with task as list of contentBlock with latest semantic conventions."""
     with mock.patch("strands.telemetry.tracer.trace_api.get_tracer", return_value=mock_tracer):
+        monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
         tracer = Tracer()
-        tracer.use_latest_genai_conventions = True
         tracer.tracer = mock_tracer
 
         mock_span = mock.MagicMock()
@@ -439,10 +439,10 @@ def test_end_swarm_span(mock_span):
     )
 
 
-def test_end_swarm_span_latest_conventions(mock_span):
+def test_end_swarm_span_latest_conventions(mock_span, monkeypatch):
     """Test ending a tool call span with latest semantic conventions."""
+    monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
     tracer = Tracer()
-    tracer.use_latest_genai_conventions = True
     swarm_final_reuslt = "foo bar bar"
 
     tracer.end_swarm_span(mock_span, swarm_final_reuslt)
@@ -503,10 +503,10 @@ def test_end_tool_call_span(mock_span):
     mock_span.end.assert_called_once()
 
 
-def test_end_tool_call_span_latest_conventions(mock_span):
+def test_end_tool_call_span_latest_conventions(mock_span, monkeypatch):
     """Test ending a tool call span with the latest semantic conventions."""
+    monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
     tracer = Tracer()
-    tracer.use_latest_genai_conventions = True
     tool_result = {"status": "success", "content": [{"text": "Tool result"}, {"json": {"foo": "bar"}}]}
 
     tracer.end_tool_call_span(mock_span, tool_result)
@@ -558,11 +558,11 @@ def test_start_event_loop_cycle_span(mock_tracer):
         assert span is not None
 
 
-def test_start_event_loop_cycle_span_latest_conventions(mock_tracer):
+def test_start_event_loop_cycle_span_latest_conventions(mock_tracer, monkeypatch):
     """Test starting an event loop cycle span with the latest semantic conventions."""
     with mock.patch("strands.telemetry.tracer.trace_api.get_tracer", return_value=mock_tracer):
+        monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
         tracer = Tracer()
-        tracer.use_latest_genai_conventions = True
         tracer.tracer = mock_tracer
 
         mock_span = mock.MagicMock()
@@ -609,10 +609,10 @@ def test_end_event_loop_cycle_span(mock_span):
     mock_span.end.assert_called_once()
 
 
-def test_end_event_loop_cycle_span_latest_conventions(mock_span):
+def test_end_event_loop_cycle_span_latest_conventions(mock_span, monkeypatch):
     """Test ending an event loop cycle span with the latest semantic conventions."""
+    monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
     tracer = Tracer()
-    tracer.use_latest_genai_conventions = True
     message = {"role": "assistant", "content": [{"text": "Response"}]}
     tool_result_message = {
         "role": "assistant",
@@ -679,11 +679,11 @@ def test_start_agent_span(mock_tracer):
         assert span is not None
 
 
-def test_start_agent_span_latest_conventions(mock_tracer):
+def test_start_agent_span_latest_conventions(mock_tracer, monkeypatch):
     """Test starting an agent span with the latest semantic conventions."""
     with mock.patch("strands.telemetry.tracer.trace_api.get_tracer", return_value=mock_tracer):
+        monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
         tracer = Tracer()
-        tracer.use_latest_genai_conventions = True
         tracer.tracer = mock_tracer
 
         mock_span = mock.MagicMock()
@@ -749,10 +749,10 @@ def test_end_agent_span(mock_span):
     mock_span.end.assert_called_once()
 
 
-def test_end_agent_span_latest_conventions(mock_span):
+def test_end_agent_span_latest_conventions(mock_span, monkeypatch):
     """Test ending an agent span with the latest semantic conventions."""
+    monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_latest_experimental")
     tracer = Tracer()
-    tracer.use_latest_genai_conventions = True
 
     # Mock AgentResult with metrics
     mock_metrics = mock.MagicMock()
@@ -1329,7 +1329,6 @@ def test_start_event_loop_cycle_span_with_tool_result_message(mock_tracer):
 def test_start_agent_span_does_not_include_tool_definitions_by_default():
     """Verify that start_agent_span does not include tool definitions by default."""
     tracer = Tracer()
-    tracer.include_tool_definitions = False
     tracer._start_span = mock.MagicMock()
 
     tools_config = {
@@ -1349,10 +1348,10 @@ def test_start_agent_span_does_not_include_tool_definitions_by_default():
     assert "gen_ai.tool.definitions" not in attributes
 
 
-def test_start_agent_span_includes_tool_definitions_when_enabled():
+def test_start_agent_span_includes_tool_definitions_when_enabled(monkeypatch):
     """Verify that start_agent_span includes tool definitions when enabled."""
+    monkeypatch.setenv("OTEL_SEMCONV_STABILITY_OPT_IN", "gen_ai_tool_definitions")
     tracer = Tracer()
-    tracer.include_tool_definitions = True
     tracer._start_span = mock.MagicMock()
 
     tools_config = {