8000 chore: enhance error messaging when MCP tools are used without sessio… by dbschmigelski · Pull Request #175 · strands-agents/sdk-python · GitHub
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chore: enhance error messaging when MCP tools are used without sessio… #175

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Merged
merged 4 commits into from
Jun 9, 2025
Merged

chore: enhance error messaging when MCP tools are used without sessio… #175

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61a1d9b
chore: enhance error messaging when MCP tools are used without sessio…
dbschmigelski Jun 4, 2025
fb1eba9
Update src/strands/tools/mcp/mcp_client.py
dbschmigelski Jun 4, 2025
95a8221
update error message with link to Troubleshooting section in docs
dbschmigelski Jun 9, 2025
f9bdda4
Merge branch 'strands-agents:main' into dea/mcp-error-messaging
dbschmigelski Jun 9, 2025
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10 changes: 8 additions & 2 deletions src/strands/tools/mcp/mcp_client.py
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,12 @@
"image/webp": "webp",
}

CLIENT_SESSION_NOT_RUNNING_ERROR_MESSAGE = (
"the client session is not running. Ensure the agent is used within "
"the MCP client context manager. For more information see: "
"https://strandsagents.com/latest/user-guide/concepts/tools/mcp-tools/#mcpclientinitializationerror"
)


class MCPClient:
"""Represents a connection to a Model Context Protocol (MCP) server.
Expand Down Expand Up @@ -145,7 +151,7 @@ def list_tools_sync(self) -> List[MCPAgentTool]:
"""
self._log_debug_with_thread("listing MCP tools synchronously")
if not self._is_session_active():
raise MCPClientInitializationError("the client session is not running")
raise MCPClientInitializationError(CLIENT_SESSION_NOT_RUNNING_ERROR_MESSAGE)

async def _list_tools_async() -> ListToolsResult:
return await self._background_thread_session.list_tools()
Expand Down Expand Up @@ -180,7 +186,7 @@ def call_tool_sync(
"""
self._log_debug_with_thread("calling MCP tool '%s' synchronously with tool_use_id=%s", name, tool_use_id)
if not self._is_session_active():
raise MCPClientInitializationError("the client session is not running")
raise MCPClientInitializationError(CLIENT_SESSION_NOT_RUNNING_ERROR_MESSAGE)

async def _call_tool_async() -> MCPCallToolResult:
return await self._background_thread_session.call_tool(name, arguments, read_timeout_seconds)
Expand Down
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