[DNM] OTEL: Instrument all MCP methods

[strawgate]

Summary

Adds OpenTelemetry span coverage for MCP list operations and enriches delegate spans with method names. Refs #3887.

• Server spans for list operations: Wraps list_tools, list_resources, list_resource_templates, and list_prompts in server_span() in src/fastmcp/server/server.py
• Client spans for list operations: Wraps list_tools_mcp, list_resources_mcp, list_resource_templates_mcp, and list_prompts_mcp in client_span() in client mixins
• mcp.method.name on delegate spans: Adds optional method parameter to delegate_span() in src/fastmcp/server/telemetry.py and propagates the MCP method name from all callers in src/fastmcp/server/providers/fastmcp_provider.py
• Tests: New test files for server list spans, client list spans, and delegate span method attributes

Test plan

• uv run ruff check src/ passes
• uv run pytest tests/server/telemetry tests/client/telemetry -x -- all 46 tests pass (18 new + 28 existing)

🤖 Generated with Claude Code

[marvin-context-protocol]

Test Failure Analysis

Summary: The ruff format check failed because 2 files in this PR have formatting that does not match ruff's style.

Root Cause: Two files were reformatted by ruff format during the CI run, indicating they were not formatted before pushing:

• src/fastmcp/server/server.py: Two server_span(...) calls are written across 3 lines each but ruff collapses them to single lines (at lines ~621 and ~1026).
• tests/client/telemetry/test_client_list_tracing.py: A list comprehension condition split across 2 lines needs to be joined onto one line (around line 70).

Suggested Solution: Run ruff format locally and commit the result:

uv run ruff format src/fastmcp/server/server.py tests/client/telemetry/test_client_list_tracing.py

Or run the full pre-commit suite to catch all issues at once:

uv run prek run --all-files

Then commit and push the reformatted files.

Detailed Analysis

The ruff format hook failed with:

ruff format.............................................Failed
- hook id: ruff-format
- files were modified by this hook
  2 files reformatted, 731 files left unchanged

Diff applied by ruff in src/fastmcp/server/server.py:

@@ -621,9 +621,7 @@
             # Core logic: list tools
-            with server_span(
-                "tools/list", "tools/list", self.name, "tool", ""
-            ):
+            with server_span("tools/list", "tools/list", self.name, "tool", ""):

@@ -1028,9 +1026,7 @@
             # Core logic: list prompts
-            with server_span(
-                "prompts/list", "prompts/list", self.name, "prompt", ""
-            ):
+            with server_span("prompts/list", "prompts/list", self.name, "prompt", ""):

Diff applied by ruff in tests/client/telemetry/test_client_list_tracing.py:

@@ -70,8 +70,7 @@
             (
                 s
                 for s in tools_list_spans
-                if s.attributes is not None
-                and "fastmcp.server.name" in s.attributes
+                if s.attributes is not None and "fastmcp.server.name" in s.attributes
             ),

(Comment edited to reflect latest analysis from workflow run 24329066788)

Related Files

• src/fastmcp/server/server.py — Two server_span() calls need to be collapsed to single lines
• tests/client/telemetry/test_client_list_tracing.py — List comprehension condition needs to be joined to one line