TASK.md

Task contract: stateless MCP JSON-RPC tool server (2026-07-28)

Change only starter/mcp_server.py.

• Implement MCPServer class:
  • register_tool(name: str, description: str, schema: dict, handler: Callable) -> None
  • handle_request(request: dict) -> dict: Processes a JSON-RPC 2.0 request dict and returns a response dict.
• JSON-RPC 2.0 compliance:
  • Must check "jsonrpc": "2.0" and preserve request "id".
  • Return error -32600 (Invalid Request) if request is not a valid dict or lacks method or jsonrpc != "2.0".
  • Return error -32601 (Method not found) if method is unknown.
• 2026-07-28 stateless behavior:
  • initialize must return -32601 with a message noting it was removed by the stateless 2026-07-28 specification; there is no handshake before tool calls.
  • If a request carries _meta.protocolVersion and it is not "2026-07-28", return -32600 (Invalid Request); requests self-describe their version.
• Supported methods:
  • "tools/list": returns {"result": {"tools": [{"name": ..., "description": ..., "inputSchema": ...}, ...]}}.
  • "tools/call": accepts params: {"name": ..., "arguments": ..., "inputResponses": {...}?} and calls the handler as handler(arguments, inputResponses).
    • If tool not registered: returns {"result": {"isError": True, "content": [{"type": "text", "text": "Tool not found"}]}}.
    • If required argument missing: returns {"result": {"isError": True, "content": [{"type": "text", "text": "Missing required argument: <arg>"}]}}.
    • If the handler raises InputRequired(requests): returns {"result": {"resultType": "input_required", "requests": <requests>, "content": [{"type": "text", "text": "Additional client input is required before this tool can finish."}]}}. The client retries the same call with answers in params.inputResponses.
    • On handler success: returns {"result": {"content": [{"type": "text", "text": str(output)}]}}.
    • On any other handler exception: catch and return {"result": {"isError": True, "content": [{"type": "text", "text": f"Error: {e}"}]}}.
• Provide InputRequired(Exception) with a requests attribute so tools can request client input.

Done means python examples/mcp-server/verify.py starter exits successfully.