splunk-otel-instrumentation-fastmcp 0.1.0

Splunk OpenTelemetry instrumentation for FastMCP (Model Context Protocol)

This library provides automatic instrumentation for FastMCP, a Python library for building Model Context Protocol (MCP) servers.

Installation

pip install splunk-otel-instrumentation-fastmcp

This can also be installed with the instruments extra to automatically install FastMCP:

pip install 'splunk-otel-instrumentation-fastmcp[instruments]'

Usage

Programmatic instrumentation:

from opentelemetry.instrumentation.fastmcp import FastMCPInstrumentor

FastMCPInstrumentor().instrument()

Auto-instrumentation:

The instrumentation is automatically applied when using OpenTelemetry auto-instrumentation:

opentelemetry-instrument python your_mcp_server.py

Environment Variables

The following environment variables control the instrumentation behavior:

• OTEL_INSTRUMENTATION_GENAI_ENABLE: Enable/disable instrumentation (default: true)

• OTEL_INSTRUMENTATION_GENAI_CAPTURE_MESSAGE_CONTENT: Capture tool arguments and results (default: false)

• OTEL_INSTRUMENTATION_GENAI_EMITTERS: Select emitters - span, metric, event (default: span)

What is Instrumented

Server-side:

• FastMCP server initialization

• Tool execution via ToolManager.call_tool

Client-side:

• FastMCP client session lifecycle

• Tool calls and listings

Transport-level:

• Automatic trace context propagation via _meta field

• Works for all MCP transports: stdio, SSE, streamable-http

Trace Context Propagation

The instrumentation automatically propagates W3C TraceContext (traceparent, tracestate) between MCP client and server processes. This enables distributed tracing across process boundaries:

• Client spans and server spans share the same trace_id

• Server tool execution spans are children of client tool call spans

• No code changes required in your MCP server or client

Telemetry

Spans:

• mcp.server - Parent span for server operations

• {tool_name}.tool - Child span for each tool execution

• mcp.client - Parent span for client session

Metrics:

• gen_ai.mcp.tool.duration - Duration of tool executions (histogram)

Events:

When content capture is enabled:

• mcp.tool.input - Tool arguments

• mcp.tool.output - Tool results

References

• FastMCP

• Model Context Protocol

• OpenTelemetry Project