Inline OTel span attributes

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 build_server_span_attributes, extract_trace_context, otel_span
+from mcp.shared._otel import 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
@@ -464,17 +464,23 @@ async def _handle_request(
             close_standalone_sse_stream_cb = message.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=build_server_span_attributes(
-                service_name=self.name,
-                method=req.method,
-                request_id=message.request_id,
-                params=req.params,
-                session_id=session_id,
-            ),
+            attributes=span_attributes,
             context=parent_context,
         ) as span:
             if handler := self._request_handlers.get(req.method):

src/mcp/shared/_otel.py

@@ -11,7 +11,6 @@
 from opentelemetry.trace import SpanKind, get_tracer
 
 _tracer = get_tracer("mcp-python-sdk")
-MCP_RPC_SYSTEM = "mcp"
 
 
 @contextmanager
@@ -35,50 +34,3 @@ 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 build_client_span_attributes, inject_trace_context, otel_span
+from mcp.shared._otel import 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
@@ -272,15 +272,19 @@ 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=build_client_span_attributes(
-                    method=request.method,
-                    request_id=request_id,
-                    params=request_data.get("params"),
-                ),
+                attributes=span_attributes,
             ):
                 # Inject W3C trace context into _meta (SEP-414).
                 meta: dict[str, Any] = request_data.setdefault("params", {}).setdefault("_meta", {})