Fix pyright type errors and coverage gaps in OTel span attributes

Author: etserend

src/mcp/shared/_otel.py

@@ -2,9 +2,9 @@
 
 from __future__ import annotations
 
-from collections.abc import Iterator
+from collections.abc import Iterator, Mapping
 from contextlib import contextmanager
-from typing import Any
+from typing import Any, cast
 
 from opentelemetry.context import Context
 from opentelemetry.propagate import extract, inject
@@ -29,15 +29,12 @@ def build_span_attributes(
     method: str,
     request_id: Any,
     *,
-    params: dict[str, Any] | None = None,
-    server_name: str | None = None,
-    session_id: str | None = None,
+    params: Mapping[str, Any] | None = None,
 ) -> dict[str, Any]:
     """Build OTel span attributes for an MCP request.
 
     Produces the base set of semantic convention attributes shared by both
     client (`SpanKind.CLIENT`) and server (`SpanKind.SERVER`) spans.
-    Pass `server_name` and `session_id` for server-side spans.
     """
     attrs: dict[str, Any] = {
         "rpc.system": "mcp",
@@ -49,27 +46,21 @@ def build_span_attributes(
     if operation is not None:
         attrs["gen_ai.operation.name"] = operation
 
-    if server_name is not None:
-        attrs["rpc.service"] = server_name
-
     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
-        uri = params.get("uri")
+        uri: Any = params.get("uri")
         if uri is None:
             ref = params.get("ref")
             if isinstance(ref, dict):
-                uri = ref.get("uri")
+                uri = cast(dict[str, Any], ref).get("uri")
         if uri is not None:
             attrs["mcp.resource.uri"] = str(uri)
 
-    if session_id is not None:
-        attrs["mcp.session.id"] = session_id
-
     return attrs
 
 

tests/shared/test_otel.py

@@ -6,10 +6,21 @@
 from mcp import types
 from mcp.client.client import Client
 from mcp.server.mcpserver import MCPServer
+from mcp.shared._otel import build_span_attributes
 
 pytestmark = pytest.mark.anyio
 
 
+def test_build_span_attributes_ref_uri() -> None:
+    """build_span_attributes extracts mcp.resource.uri from nested ref.uri."""
+    attrs = build_span_attributes(
+        "completion/complete",
+        "1",
+        params={"ref": {"uri": "test://doc"}},
+    )
+    assert attrs["mcp.resource.uri"] == "test://doc"
+
+
 async def test_client_and_server_spans(capfire: CaptureLogfire):
     """Verify that calling a tool produces client and server spans with correct attributes."""
     server = MCPServer("test")
@@ -55,11 +66,6 @@ async def test_list_tools_spans(capfire: CaptureLogfire):
     """Verify that listing tools produces spans with list_tools operation."""
     server = MCPServer("test")
 
-    @server.tool()
-    def greet(name: str) -> str:
-        """Greet someone."""
-        return f"Hello, {name}!"
-
     async with Client(server) as client:
         await client.list_tools()