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fastmcp.telemetry

OpenTelemetry instrumentation for FastMCP. This module provides native OpenTelemetry integration for FastMCP servers and clients. It uses only the opentelemetry-api package, so telemetry is a no-op unless the user installs an OpenTelemetry SDK and configures exporters. Example usage with SDK: 
from opentelemetry import trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import ConsoleSpanExporter, SimpleSpanProcessor

# Configure the SDK (user responsibility)
provider = TracerProvider()
provider.add_span_processor(SimpleSpanProcessor(ConsoleSpanExporter()))
trace.set_tracer_provider(provider)

# Now FastMCP will emit traces
from fastmcp import FastMCP
mcp = FastMCP("my-server")

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Functions

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get_tracer 

get_tracer(version: str | None = None) -> Tracer
Get the FastMCP tracer for creating spans. Args:
  • version: Optional version string for the instrumentation
Returns:
  • A tracer instance. Returns a no-op tracer if no SDK is configured.

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inject_trace_context 

inject_trace_context(meta: dict[str, Any] | None = None) -> dict[str, Any] | None
Inject current trace context into a meta dict for MCP request propagation. Args:
  • meta: Optional existing meta dict to merge with trace context
Returns:
  • A new dict containing the original meta (if any) plus trace context keys,
  • or None if no trace context to inject and meta was None

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record_span_error 

record_span_error(span: Span, exception: BaseException) -> None
Record an exception on a span and set error status.

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extract_trace_context 

extract_trace_context(meta: dict[str, Any] | None) -> Context
Extract trace context from an MCP request meta dict. If already in a valid trace (e.g., from HTTP propagation), the existing trace context is preserved and meta is not used. Args:
  • meta: The meta dict from an MCP request (ctx.request_context.meta)
Returns:
  • An OpenTelemetry Context with the extracted trace context,
  • or the current context if no trace context found or already in a trace