fix: remove resource URI from span names to avoid high-cardinality

Per MCP semantic conventions, resource URIs SHOULD NOT be included in
span names by default since they can be unbounded (especially with
templates like users://{id}/profile). The URI remains available via
the mcp.resource.uri attribute.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/fastmcp/client/mixins/resources.py

@@ -205,7 +205,7 @@ class ClientResourcesMixin:
         """
         uri_str = str(uri)
         with client_span(
-            f"resources/read {uri_str}",
+            "resources/read",
             "resources/read",
             uri_str,
             session_id=self.transport.get_session_id(),

src/fastmcp/server/providers/proxy.py

@@ -238,7 +238,7 @@ class ProxyResource(Resource):
 
         backend_uri = self._backend_uri or str(self.uri)
         with client_span(
-            f"resources/read {backend_uri}",
+            "resources/read",
             "resources/read",
             backend_uri,
             resource_uri=backend_uri,

src/fastmcp/server/server.py

@@ -1362,7 +1362,7 @@ class FastMCP(
 
             # Core logic: find and read resource (providers queried in parallel)
             with server_span(
-                f"resources/read {uri}",
+                "resources/read",
                 "resources/read",
                 self.name,
                 "resource",

tests/client/telemetry/test_client_tracing.py

@@ -128,8 +128,8 @@ class TestClientResourceTracing:
         spans = trace_exporter.get_finished_spans()
         span_names = [s.name for s in spans]
 
-        # Client should create "resources/read data://config" span
-        assert "resources/read data://config" in span_names
+        # Client should create "resources/read" span (URI in attributes, not name)
+        assert "resources/read" in span_names
 
     async def test_read_resource_span_attributes(
         self, trace_exporter: InMemorySpanExporter
@@ -151,7 +151,7 @@ class TestClientResourceTracing:
             (
                 s
                 for s in spans
-                if s.name.startswith("resources/read data://")
+                if s.name == "resources/read"
                 and s.attributes is not None
                 and "fastmcp.server.name" not in s.attributes
             ),
@@ -420,7 +420,7 @@ class TestClientErrorTracing:
             (
                 s
                 for s in spans
-                if s.name.startswith("resources/read data://fail")
+                if s.name == "resources/read"
                 and s.attributes is not None
                 and "fastmcp.server.name" not in s.attributes
             ),
@@ -431,7 +431,7 @@ class TestClientErrorTracing:
             (
                 s
                 for s in spans
-                if s.name.startswith("resources/read data://fail")
+                if s.name == "resources/read"
                 and s.attributes is not None
                 and "fastmcp.server.name" in s.attributes
             ),

tests/server/telemetry/test_server_tracing.py

@@ -104,7 +104,7 @@ class TestResourceTracing:
         assert len(spans) == 1
 
         span = spans[0]
-        assert span.name == "resources/read config://app"
+        assert span.name == "resources/read"
         assert span.kind == SpanKind.SERVER
         assert span.attributes is not None
         # Standard MCP semantic conventions
@@ -135,7 +135,7 @@ class TestResourceTracing:
         assert len(spans) == 1
 
         span = spans[0]
-        assert span.name == "resources/read users://123/profile"
+        assert span.name == "resources/read"
         assert span.kind == SpanKind.SERVER
         assert span.attributes is not None
         # Standard MCP semantic conventions
@@ -163,7 +163,7 @@ class TestResourceTracing:
         assert len(spans) == 1
 
         span = spans[0]
-        assert span.name == "resources/read nonexistent://resource"
+        assert span.name == "resources/read"
         assert span.status.status_code == StatusCode.ERROR