How opentel-mcp compares
opentel-mcp is a purpose-built OpenTelemetry instrumentation layer for Model Context Protocol (MCP) servers on Node.js. The closest points of comparison are raw @opentelemetry/api instrumentation written by hand, and — for a narrower, specific reason explained below — fastmcp, a Python MCP framework.
TL;DR
Raw@opentelemetry/api gives you spans if you write the wrapping code yourself, but has no idea what a CallToolResult is — it can't see isError: true without you writing a check for it. fastmcp is a separate, Python-based project; it isn't a same-ecosystem alternative to a Node.js package, and the only confirmed connection is a bug report, not a feature comparison. No dedicated MCP-focused tracing library under the name "mcp-tracer" was found on npm or GitHub — it isn't included in the table below.How does opentel-mcp compare to raw @opentelemetry/api?
Raw @opentelemetry/api is a general-purpose tracing and metrics API — it has no concept of MCP, JSON-RPC 2.0, or CallToolResult. That's true by definition, not a knock against it: it's not an MCP library. To get a span per tool call with it, you write the tracer.startActiveSpan() wrapping yourself, around every handler — see the Migration Guide for exactly what that code looks like. That hand-written wrapper will catch a thrown exception if you write a try/catch around it, same as opentel-mcp does. It will not catch isError: true unless you specifically write a check for it — see Silent Failures for why that check is easy to miss.
How does opentel-mcp compare to fastmcp?
fastmcp (PrefectHQ/fastmcp) is a Python framework for building MCP servers. opentel-mcp is a Node.js package that instruments servers built on @modelcontextprotocol/sdk, the JavaScript/TypeScript MCP SDK. It cannot instrument a Python process — different language runtime entirely, so a feature-by-feature comparison table between the two isn't really meaningful, and this page won't fabricate one.
The confirmed connection between the two projects: while working on MCP observability, opentel-mcp's author found and reported a silent-failure-propagation bug in fastmcp itself (PrefectHQ/fastmcp#4549, fixed in PR #4587). That's an upstream bug report and fix, not a compatibility claim — fastmcp's own OpenTelemetry integration, if any, hasn't been independently verified here, and isn't in the table below for that reason.
What about mcp-tracer or other MCP-specific tracing libraries?
Checked both the npm registry and GitHub for a library named "mcp-tracer" — nothing matching an MCP-focused OpenTelemetry or tracing library came up under that name on either. If a real one exists under a different name, this page doesn't know about it; it isn't included in the table below rather than being represented by a guess.
Full comparison table
| Capability | opentel-mcp | @opentelemetry/api (raw) |
|---|---|---|
| Instruments tools/call automatically | ||
| Detects isError: true inside a successful response | ||
| Deep failure fingerprinting | ||
| Built-in mcp.tool.* metrics instruments | ||
| Cardinality-safe metric attributes, structurally enforced | ||
| Never throws into the instrumented handler | ||
| Instruments resources/prompts (not just tools) | ||
| Requires manual span code per handler | ||
| MIT licensed |
“Unverified” means a claim this page can't back up with source or spec evidence, not a claim of “no.” fastmcp and mcp-tracer are intentionally not columns here — see the sections above for why.
When is raw @opentelemetry/api enough on its own?
If silent failures aren't a concern for a given server — every tool either succeeds cleanly or throws, never returning isError: true on a JSON-RPC success — a hand-written span wrapper around thrown exceptions covers the same ground opentel-mcp does for that case. The gap opentel-mcp exists to close is specifically the isError: true case, plus not having to write and maintain that wrapping code by hand across every tool handler.
By Thirumalaiboobathi B — Last updated: July 26, 2026
Where do I go from here?
- Silent Failures — the detection gap this whole comparison centers on.
- Migration Guide — moving from hand-written @opentelemetry/api instrumentation.
- FAQ — including the fastmcp question in more detail.