Fix(Tool): Class method with @tool decorator is also accepted as a valid Tool.

.gitignore

@@ -8,4 +8,5 @@ __pycache__*
 .ruff_cache
 *.bak
 .vscode
-dist
+dist
+.idea

src/strands/agent/conversation_manager/sliding_window_conversation_manager.py

@@ -140,7 +140,7 @@ def reduce_context(self, agent: "Agent", e: Optional[Exception] = None) -> None:
             if results_truncated:
                 logger.debug("message_index=<%s> | tool results truncated", last_message_idx_with_tool_results)
                 return
-        
+
         # Try to trim index id when tool result cannot be truncated anymore
         # If the number of messages is less than the window_size, then we default to 2, otherwise, trim to window size
         trim_index = 2 if len(messages) <= self.window_size else len(messages) - self.window_size

src/strands/tools/registry.py

@@ -92,8 +92,8 @@ def process_tools(self, tools: List[Any]) -> List[str]:
                     if not function_tools:
                         logger.warning("tool_name=<%s>, module_path=<%s> | invalid agent tool", tool_name, module_path)
 
-            # Case 5: Function decorated with @tool
-            elif inspect.isfunction(tool) and hasattr(tool, "TOOL_SPEC"):
+            # Case 5: Function or Method decorated with @tool
+            elif (inspect.isfunction(tool) or inspect.ismethod(tool)) and hasattr(tool, "TOOL_SPEC"):
                 try:
                     function_tool = FunctionTool(tool)
                     logger.debug("tool_name=<%s> | registering function tool", function_tool.tool_name)

tests-integ/test_mcp_client.py

@@ -104,8 +104,8 @@ def test_can_reuse_mcp_client():
 
 
 @pytest.mark.skipif(
-    condition=os.environ.get("GITHUB_ACTIONS") == 'true',
-    reason="streamable transport is failing in GitHub actions, debugging if linux compatibility issue"
+    condition=os.environ.get("GITHUB_ACTIONS") == "true",
+    reason="streamable transport is failing in GitHub actions, debugging if linux compatibility issue",
 )
 def test_streamable_http_mcp_client():
     server_thread = threading.Thread(

tests/strands/tools/test_registry.py

@@ -6,6 +6,7 @@
 
 import pytest
 
+from strands import tool
 from strands.tools import PythonAgentTool
 from strands.tools.registry import ToolRegistry
 
@@ -43,3 +44,25 @@ def test_register_tool_with_similar_name_raises():
         str(err.value) == "Tool name 'tool_like_this' already exists as 'tool-like-this'. "
         "Cannot add a duplicate tool which differs by a '-' or '_'"
     )
+
+
+@pytest.fixture
+def test_agent():
+    class TestAgent:
+        @tool
+        def word_counter(self, text: str) -> str:
+            """Count words in text"""
+            return f"Word count: {len(text.split())}"
+
+    return TestAgent()
+
+
+@pytest.fixture
+def tool_registry():
+    return ToolRegistry()
+
+
+def test_class_method_register_tool(test_agent, tool_registry):
+    registered_tool_names = tool_registry.process_tools([test_agent.word_counter])
+    assert len(registered_tool_names) == 1
+    assert registered_tool_names[0] == "word_counter"