server: make MCP test fixtures JSON-RPC 2.0 compliant

Add the missing notification guard to mcp_malformed_server.py and
mcp_burst_server.py (the latter treated id 0 as a notification and
replied to unknown ones; its notification table is now unused).

Return -32602 instead of -32601 for unknown tools: tools/call is a
valid method, the tool name is the invalid parameter.

Also fix the test module docstring: tools are named <server>_<tool>.

(cherry picked from commit 74a08e8c311dabf3b49d06cc6d754b0097ae7a38)

Assisted-by: Claude Opus 4.8

tools/server/tests/fixtures/mcp_burst_server.py

@@ -66,7 +66,7 @@ def handle_tools_call(params, req_id):
         response = {
             "jsonrpc": "2.0",
             "id": req_id,
-            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+            "error": {"code": -32602, "message": f"Unknown tool: {tool_name}"}
         }
         return response
 
@@ -76,11 +76,6 @@ HANDLERS = {
     "tools/call": handle_tools_call,
 }
 
-# notifications have no id and don't expect a response
-NOTIFICATION_HANDLERS = {
-    "notifications/initialized": lambda params, req_id: None,
-}
-
 def main():
     # Use line-buffered text mode for regular responses, but the burst write
     # uses os.write() directly to guarantee a single kernel write().
@@ -100,9 +95,8 @@ def main():
         req_id = request.get("id")
         params = request.get("params", {})
 
-        # Check notification handlers first (no response expected)
-        if not req_id and method in NOTIFICATION_HANDLERS:
-            NOTIFICATION_HANDLERS[method](params, req_id)
+        # JSON-RPC 2.0: a message without an id is a notification and must not receive a response
+        if req_id is None:
             continue
 
         handler = HANDLERS.get(method)

tools/server/tests/fixtures/mcp_crash_server.py

@@ -67,7 +67,7 @@ def handle_tools_call(params, req_id):
         return {
             "jsonrpc": "2.0",
             "id": req_id,
-            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+            "error": {"code": -32602, "message": f"Unknown tool: {tool_name}"}
         }
 
 HANDLERS = {

tools/server/tests/fixtures/mcp_grandchild_server.py

@@ -56,7 +56,7 @@ def handle_tools_call(params, req_id):
             "id": req_id,
             "result": {"content": [{"type": "text", "text": f"echo: {message}"}]},
         }
-    return {"jsonrpc": "2.0", "id": req_id, "error": {"code": -32601, "message": "Unknown tool"}}
+    return {"jsonrpc": "2.0", "id": req_id, "error": {"code": -32602, "message": "Unknown tool"}}
 
 
 HANDLERS = {

tools/server/tests/fixtures/mcp_malformed_server.py

@@ -63,7 +63,7 @@ def handle_tools_call(params, req_id):
         return {
             "jsonrpc": "2.0",
             "id": req_id,
-            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+            "error": {"code": -32602, "message": f"Unknown tool: {tool_name}"}
         }
 
 HANDLERS = {
@@ -92,6 +92,10 @@ def main():
         req_id = request.get("id")
         params = request.get("params", {})
 
+        # JSON-RPC 2.0: a message without an id is a notification and must not receive a response
+        if req_id is None:
+            continue
+
         handler = HANDLERS.get(method)
         if handler:
             response = handler(params, req_id)

tools/server/tests/fixtures/mcp_slow_server.py

@@ -58,7 +58,7 @@ def handle_tools_call(params, req_id):
         return {
             "jsonrpc": "2.0",
             "id": req_id,
-            "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+            "error": {"code": -32602, "message": f"Unknown tool: {tool_name}"}
         }
 
 HANDLERS = {
@@ -92,7 +92,7 @@ def main():
             return {
                 "jsonrpc": "2.0",
                 "id": req_id,
-                "error": {"code": -32601, "message": f"Unknown tool: {tool_name}"}
+                "error": {"code": -32602, "message": f"Unknown tool: {tool_name}"}
             }
 
     sys.stdout = os.fdopen(sys.stdout.fileno(), "w", buffering=1)

tools/server/tests/unit/test_mcp_servers.py

@@ -4,7 +4,7 @@ Tests for MCP server integration via the /tools endpoint.
 
 Invariants verified:
 1. MCP tools appear in /tools listing when configured
-2. MCP tools use <server>:<tool> naming
+2. MCP tools use <server>_<tool> naming
 3. MCP tools can be invoked and return correct results
 4. Misconfigured MCP servers do not crash the server
 5. Multiple MCP servers can be configured simultaneously