Make opentelemetry-api a mandatory dependency

Simplify _otel.py by removing the ImportError fallback and lru_cache
since opentelemetry-api is now always available.

Author: Kludex

pyproject.toml

@@ -40,13 +40,13 @@ dependencies = [
     "pyjwt[crypto]>=2.10.1",
     "typing-extensions>=4.13.0",
     "typing-inspection>=0.4.1",
+    "opentelemetry-api>=1.28.0",
 ]
 
 [project.optional-dependencies]
 rich = ["rich>=13.9.4"]
 cli = ["typer>=0.16.0", "python-dotenv>=1.0.0"]
 ws = ["websockets>=15.0.1"]
-otel = ["opentelemetry-api>=1.28.0"]
 
 [project.scripts]
 mcp = "mcp.cli:app [cli]"
@@ -58,7 +58,7 @@ required-version = ">=0.9.5"
 [dependency-groups]
 dev = [
     # We add mcp[cli,ws] so `uv sync` considers the extras.
-    "mcp[cli,ws,otel]",
+    "mcp[cli,ws]",
     "pyright>=1.1.400",
     "pytest>=8.3.4",
     "ruff>=0.8.5",

src/mcp/shared/_otel.py

@@ -1,26 +1,14 @@
-"""OpenTelemetry helpers for MCP.
-
-Provides a context manager that creates an OpenTelemetry span when
-``opentelemetry-api`` is installed, or acts as a no-op otherwise.
-"""
+"""OpenTelemetry helpers for MCP."""
 
 from __future__ import annotations
 
-import functools
 from collections.abc import Iterator
 from contextlib import contextmanager
 from typing import Any
 
+from opentelemetry.trace import SpanKind, get_tracer
 
-@functools.lru_cache(maxsize=1)
-def _get_tracer() -> Any:
-    """Return the OTel tracer for ``mcp``, or ``None``."""
-    try:
-        from opentelemetry.trace import get_tracer
-
-        return get_tracer("mcp-python-sdk")
-    except ImportError:
-        return None
+_tracer = get_tracer("mcp-python-sdk")
 
 
 @contextmanager
@@ -30,14 +18,7 @@ def otel_span(
     kind: str = "INTERNAL",
     attributes: dict[str, Any] | None = None,
 ) -> Iterator[Any]:
-    """Create an OTel span if ``opentelemetry-api`` is installed, else no-op."""
-    tracer = _get_tracer()
-    if tracer is None:
-        yield None
-        return
-
-    from opentelemetry.trace import SpanKind
-
+    """Create an OTel span."""
     span_kind = getattr(SpanKind, kind, SpanKind.INTERNAL)
-    with tracer.start_as_current_span(name, kind=span_kind, attributes=attributes) as span:
+    with _tracer.start_as_current_span(name, kind=span_kind, attributes=attributes) as span:
         yield span

tests/shared/test_otel.py

@@ -1,24 +1,12 @@
 from __future__ import annotations
 
-from unittest.mock import patch
-
 import pytest
 
-from mcp.shared._otel import _get_tracer, otel_span
+from mcp.shared._otel import otel_span
 
 pytestmark = pytest.mark.anyio
 
 
 def test_otel_span_creates_span():
-    _get_tracer.cache_clear()
     with otel_span("test.span", kind="CLIENT", attributes={"key": "value"}) as span:
         assert span is not None
-
-
-def test_otel_span_noop_when_unavailable():
-    _get_tracer.cache_clear()
-    with patch.dict("sys.modules", {"opentelemetry": None, "opentelemetry.trace": None}):
-        _get_tracer.cache_clear()
-        with otel_span("test.span") as span:
-            assert span is None
-    _get_tracer.cache_clear()