Address review: restrict gen_ai.operation.name to tools/call per spec, add gen_ai.prompt.name for prompts/get

Author: etserend

src/mcp/shared/_otel.py

@@ -12,19 +12,6 @@
 
 _tracer = get_tracer("mcp-python-sdk")
 
-# Maps MCP JSON-RPC method names to GenAI semantic convention operation names.
-# https://github.com/open-telemetry/semantic-conventions-genai/blob/main/docs/gen-ai/mcp.md
-_METHOD_TO_GEN_AI_OPERATION: dict[str, str] = {
-    "tools/call": "execute_tool",
-    "tools/list": "list_tools",
-    "resources/read": "read_resource",
-    "resources/list": "list_resources",
-    "resources/templates/list": "list_resources",
-    "prompts/get": "get_prompt",
-    "prompts/list": "list_prompts",
-}
-
-
 def build_span_attributes(
     method: str,
     request_id: Any,
@@ -35,24 +22,32 @@ def build_span_attributes(
 
     Produces the base set of semantic convention attributes shared by both
     client (`SpanKind.CLIENT`) and server (`SpanKind.SERVER`) spans.
+
+    Per the GenAI MCP semconv spec, `gen_ai.operation.name` SHOULD be set to
+    `execute_tool` for `tools/call` and SHOULD NOT be set for other methods.
+    https://github.com/open-telemetry/semantic-conventions/blob/main/docs/gen-ai/mcp.md
     """
     attrs: dict[str, Any] = {
         "rpc.system": "mcp",
         "mcp.method.name": method,
         "jsonrpc.request.id": str(request_id),
     }
 
-    operation = _METHOD_TO_GEN_AI_OPERATION.get(method)
-    if operation is not None:
-        attrs["gen_ai.operation.name"] = operation
-
     if params is not None:
-        # gen_ai.tool.name — present on tools/call, prompts/get
-        name = params.get("name")
-        if isinstance(name, str):
-            attrs["gen_ai.tool.name"] = name
-
-        # mcp.resource.uri — present on resources/read; also on completion/complete via ref.uri
+        if method == "tools/call":
+            # gen_ai.operation.name SHOULD be set to execute_tool for tools/call only.
+            attrs["gen_ai.operation.name"] = "execute_tool"
+            name = params.get("name")
+            if isinstance(name, str):
+                attrs["gen_ai.tool.name"] = name
+
+        elif method == "prompts/get":
+            name = params.get("name")
+            if isinstance(name, str):
+                attrs["gen_ai.prompt.name"] = name
+
+        # mcp.resource.uri — resources/read, resources/subscribe, resources/unsubscribe,
+        # notifications/resources/updated, and completion/complete via ref.uri
         uri: Any = params.get("uri")
         if uri is None:
             ref = params.get("ref")

tests/shared/test_otel.py

@@ -19,6 +19,21 @@ def test_build_span_attributes_ref_uri() -> None:
         params={"ref": {"uri": "test://doc"}},
     )
     assert attrs["mcp.resource.uri"] == "test://doc"
+    assert "gen_ai.operation.name" not in attrs
+
+
+def test_build_span_attributes_tools_call_no_name() -> None:
+    """tools/call without a name param omits gen_ai.tool.name."""
+    attrs = build_span_attributes("tools/call", "1", params={})
+    assert attrs["gen_ai.operation.name"] == "execute_tool"
+    assert "gen_ai.tool.name" not in attrs
+
+
+def test_build_span_attributes_prompts_get_no_name() -> None:
+    """prompts/get without a name param omits gen_ai.prompt.name."""
+    attrs = build_span_attributes("prompts/get", "1", params={})
+    assert "gen_ai.prompt.name" not in attrs
+    assert "gen_ai.operation.name" not in attrs
 
 
 async def test_client_and_server_spans(capfire: CaptureLogfire):
@@ -52,7 +67,7 @@ def greet(name: str) -> str:
     assert server_span["attributes"]["rpc.system"] == "mcp"
     assert server_span["attributes"]["mcp.method.name"] == "tools/call"
 
-    # GenAI semconv attributes
+    # GenAI semconv attributes — execute_tool only on tools/call
     assert client_span["attributes"]["gen_ai.operation.name"] == "execute_tool"
     assert client_span["attributes"]["gen_ai.tool.name"] == "greet"
     assert server_span["attributes"]["gen_ai.operation.name"] == "execute_tool"
@@ -63,7 +78,7 @@ def greet(name: str) -> str:
 
 
 async def test_list_tools_spans(capfire: CaptureLogfire):
-    """Verify that listing tools produces spans with list_tools operation."""
+    """Verify that listing tools produces spans without gen_ai.operation.name."""
     server = MCPServer("test")
 
     async with Client(server) as client:
@@ -74,9 +89,9 @@ async def test_list_tools_spans(capfire: CaptureLogfire):
     client_span = next(s for s in spans if s["name"] == "MCP send tools/list")
     server_span = next(s for s in spans if s["name"] == "MCP handle tools/list")
 
-    assert client_span["attributes"]["gen_ai.operation.name"] == "list_tools"
-    assert server_span["attributes"]["gen_ai.operation.name"] == "list_tools"
-    # No tool name on list — no specific tool targeted
+    # gen_ai.operation.name SHOULD NOT be set for non-tool-call methods per spec
+    assert "gen_ai.operation.name" not in client_span["attributes"]
+    assert "gen_ai.operation.name" not in server_span["attributes"]
     assert "gen_ai.tool.name" not in client_span["attributes"]
     assert "gen_ai.tool.name" not in server_span["attributes"]
 
@@ -99,9 +114,36 @@ def greeting() -> str:
     client_span = next(s for s in spans if s["name"] == "MCP send resources/read")
     server_span = next(s for s in spans if s["name"] == "MCP handle resources/read")
 
-    assert client_span["attributes"]["gen_ai.operation.name"] == "read_resource"
     assert client_span["attributes"]["mcp.resource.uri"] == "test://greeting"
-    assert server_span["attributes"]["gen_ai.operation.name"] == "read_resource"
     assert server_span["attributes"]["mcp.resource.uri"] == "test://greeting"
+    # gen_ai.operation.name SHOULD NOT be set for resources/read per spec
+    assert "gen_ai.operation.name" not in client_span["attributes"]
+    assert "gen_ai.operation.name" not in server_span["attributes"]
+
+    assert server_span["context"]["trace_id"] == client_span["context"]["trace_id"]
+
+
+async def test_prompt_get_spans(capfire: CaptureLogfire):
+    """Verify that getting a prompt produces spans with gen_ai.prompt.name."""
+    server = MCPServer("test")
+
+    @server.prompt()
+    def summarize() -> str:
+        """Summarize text."""
+        return "Summarize the following: "
+
+    async with Client(server) as client:
+        await client.get_prompt("summarize", {})
+
+    spans = capfire.exporter.exported_spans_as_dict()
+
+    client_span = next(s for s in spans if s["name"] == "MCP send prompts/get summarize")
+    server_span = next(s for s in spans if s["name"] == "MCP handle prompts/get summarize")
+
+    assert client_span["attributes"]["gen_ai.prompt.name"] == "summarize"
+    assert server_span["attributes"]["gen_ai.prompt.name"] == "summarize"
+    # gen_ai.operation.name SHOULD NOT be set for prompts/get per spec
+    assert "gen_ai.operation.name" not in client_span["attributes"]
+    assert "gen_ai.operation.name" not in server_span["attributes"]
 
     assert server_span["context"]["trace_id"] == client_span["context"]["trace_id"]