Restore OTel span attribute helpers

Author: Kludex

src/mcp/server/lowlevel/server.py

@@ -66,7 +66,7 @@ async def main():
 from mcp.server.streamable_http import EventStore
 from mcp.server.streamable_http_manager import StreamableHTTPASGIApp, StreamableHTTPSessionManager
 from mcp.server.transport_security import TransportSecuritySettings
-from mcp.shared._otel import extract_trace_context, otel_span
+from mcp.shared._otel import build_server_span_attributes, extract_trace_context, otel_span
 from mcp.shared._stream_protocols import ReadStream, WriteStream
 from mcp.shared.exceptions import MCPError
 from mcp.shared.message import ServerMessageMetadata, SessionMessage
@@ -455,32 +455,28 @@ async def _handle_request(
         # Extract W3C trace context from _meta (SEP-414).
         meta = cast(dict[str, Any] | None, getattr(req.params, "meta", None)) if req.params else None
         parent_context = extract_trace_context(meta) if meta is not None else None
-        request_data = None
+        server_message_metadata = (
+            message.message_metadata if isinstance(message.message_metadata, ServerMessageMetadata) else None
+        )
+        request_data = server_message_metadata.request_context if server_message_metadata is not None else None
         close_sse_stream_cb = None
         close_standalone_sse_stream_cb = None
-        if message.message_metadata is not None and isinstance(message.message_metadata, ServerMessageMetadata):
-            request_data = message.message_metadata.request_context
-            close_sse_stream_cb = message.message_metadata.close_sse_stream
-            close_standalone_sse_stream_cb = message.message_metadata.close_standalone_sse_stream
+        if server_message_metadata is not None:
+            close_sse_stream_cb = server_message_metadata.close_sse_stream
+            close_standalone_sse_stream_cb = server_message_metadata.close_standalone_sse_stream
         request_headers = getattr(request_data, "headers", None)
         session_id = request_headers.get(MCP_SESSION_ID_HEADER) if request_headers is not None else None
-        span_attributes: dict[str, Any] = {
-            "rpc.system": "mcp",
-            "rpc.service": self.name,
-            "rpc.method": req.method,
-            "mcp.method.name": req.method,
-            "jsonrpc.request.id": message.request_id,
-        }
-        resource_uri = getattr(req.params, "uri", None)
-        if resource_uri is not None:
-            span_attributes["mcp.resource.uri"] = str(resource_uri)
-        if session_id is not None:
-            span_attributes["mcp.session.id"] = session_id
 
         with otel_span(
             span_name,
             kind=SpanKind.SERVER,
-            attributes=span_attributes,
+            attributes=build_server_span_attributes(
+                service_name=self.name,
+                method=req.method,
+                request_id=message.request_id,
+                params=req.params,
+                session_id=session_id,
+            ),
             context=parent_context,
         ) as span:
             if handler := self._request_handlers.get(req.method):

src/mcp/shared/_otel.py

@@ -11,6 +11,7 @@
 from opentelemetry.trace import SpanKind, get_tracer
 
 _tracer = get_tracer("mcp-python-sdk")
+MCP_RPC_SYSTEM = "mcp"
 
 
 @contextmanager
@@ -34,3 +35,50 @@ def inject_trace_context(meta: dict[str, Any]) -> None:
 def extract_trace_context(meta: dict[str, Any]) -> Context:
     """Extract W3C trace context from a `_meta` dict."""
     return extract(meta)
+
+
+def build_client_span_attributes(
+    *,
+    method: str,
+    request_id: str | int,
+    params: dict[str, Any] | None = None,
+) -> dict[str, Any]:
+    """Build OTel attributes for an MCP client request span."""
+    attributes: dict[str, Any] = {
+        "rpc.system": MCP_RPC_SYSTEM,
+        "rpc.method": method,
+        "mcp.method.name": method,
+        "jsonrpc.request.id": request_id,
+    }
+
+    if params is not None and (resource_uri := params.get("uri")) is not None:
+        attributes["mcp.resource.uri"] = resource_uri
+
+    return attributes
+
+
+def build_server_span_attributes(
+    *,
+    service_name: str,
+    method: str,
+    request_id: str | int,
+    params: Any = None,
+    session_id: str | None = None,
+) -> dict[str, Any]:
+    """Build OTel attributes for an MCP server request span."""
+    attributes: dict[str, Any] = {
+        "rpc.system": MCP_RPC_SYSTEM,
+        "rpc.service": service_name,
+        "rpc.method": method,
+        "mcp.method.name": method,
+        "jsonrpc.request.id": request_id,
+    }
+
+    resource_uri = getattr(params, "uri", None)
+    if resource_uri is not None:
+        attributes["mcp.resource.uri"] = str(resource_uri)
+
+    if session_id is not None:
+        attributes["mcp.session.id"] = session_id
+
+    return attributes

src/mcp/shared/session.py

@@ -13,7 +13,7 @@
 from pydantic import BaseModel, TypeAdapter
 from typing_extensions import Self
 
-from mcp.shared._otel import inject_trace_context, otel_span
+from mcp.shared._otel import build_client_span_attributes, inject_trace_context, otel_span
 from mcp.shared._stream_protocols import ReadStream, WriteStream
 from mcp.shared.exceptions import MCPError
 from mcp.shared.message import MessageMetadata, ServerMessageMetadata, SessionMessage
@@ -272,19 +272,15 @@ async def send_request(
         try:
             target = request_data.get("params", {}).get("name")
             span_name = f"MCP send {request.method} {target}" if target else f"MCP send {request.method}"
-            span_attributes: dict[str, Any] = {
-                "rpc.system": "mcp",
-                "rpc.method": request.method,
-                "mcp.method.name": request.method,
-                "jsonrpc.request.id": request_id,
-            }
-            if (resource_uri := request_data.get("params", {}).get("uri")) is not None:
-                span_attributes["mcp.resource.uri"] = resource_uri
 
             with otel_span(
                 span_name,
                 kind=SpanKind.CLIENT,
-                attributes=span_attributes,
+                attributes=build_client_span_attributes(
+                    method=request.method,
+                    request_id=request_id,
+                    params=request_data.get("params"),
+                ),
             ):
                 # Inject W3C trace context into _meta (SEP-414).
                 meta: dict[str, Any] = request_data.setdefault("params", {}).setdefault("_meta", {})