MCPJam Docs - MCPJam Inspector

MCPJam is the open-source testing and evaluations platform for developers shipping MCP servers, MCP apps, and ChatGPT apps. Interactively test and debug tools, prompts, resources, and OAuth across 16 client configurations and 170+ LLMs, with every JSON-RPC message visible. Run evals on test cases, track accuracy over time, and gate regressions before they reach production.

MCPJam Inspector playground comparing one prompt across Claude, ChatGPT, and Copilot

Four ways to get started

Get started by testing with our hosted app, or test locally on your machine.

Inspector

On your machine. An IDE-style workspace for MCP development, with STDIO servers, tunneling, skills, and tasks. Tests local servers over STDIO and HTTP.

npx @mcpjam/inspector@latest

or install the desktop app

CLI

In your shell or CI. Connectivity, OAuth, conformance, and tool runs with JUnit/JSON output. Tests local servers over STDIO (--command) and HTTP (--url).

npm i -g @mcpjam/cli

SDK

In your test suite. Unit tests, e2e tests, and evals in TypeScript with Jest or Vitest. Spawns local STDIO servers or connects over HTTP.

npm install @mcpjam/sdk

Hosted

In your browser. Open app.mcpjam.com, click Add server, and enter your server’s URL. HTTPS only — STDIO and localhost servers need the Inspector.

What you can build

Debug an MCP server end-to-end

Connect any HTTP, HTTPS, or STDIO server, watch every JSON-RPC message live in the Playground, and inspect tool input/output, widget state, and CSP activity per call.Open the Playground → · JSON-RPC logger →

Build an MCP App or ChatGPT App widget

Validate OAuth conformance across protocol versions

Step through every stage of the MCP authorization flow against protocol versions 03-26, 06-18, 11-25, and 2026-07-28 (Latest), with DCR, pre-registration, and CIMD coverage.Guided OAuth → · CLI OAuth conformance →

Run evals across LLMs and gate CI on regressions

Author cases with expected tool calls, optional expected outputs, and deterministic checks. Run across Claude, GPT, Gemini, and your own providers — or move the same suite into Jest/Vitest with @mcpjam/sdk.Evaluate in Inspector → · Run evals from the SDK → · CI integration →

Auto-launch Inspector from your dev workflow

Launch the Inspector with a prefilled server URL, bearer token, and starting tab via CLI flags — wire it into your dev script or a framework integration.Launch from code →

Capabilities at a glance

Capability	Description
Playground	IDE-style workspace combining chat, manual tool calls, widget rendering, Chat/Trace/Raw views, and multi-model and multi-host compare. OpenAI Apps SDK and MCP App UIs, text tools, Chrome DevTools-style widget emulator. Read more
OAuth Debugger	Guided MCP OAuth conformance checks: protocol versions 03-26, 06-18, 11-25, 2026-07-28 (Latest); DCR, client pre-registration, CIMD. Read more
MCP Server Debugging	Manually run tools, resources, templates, and elicitation; full JSON-RPC logs.
Skills	Skills in the Playground, read from your local filesystem or from a project. Read more
Projects	Shared server groups with real-time team sync. Read more
Evals	Test cases with expected tool calls, run across LLMs, metrics. Read more
CLI	Run MCPJam checks, probes, and evals from the terminal. Perfect for local dev loops and CI. Read more
SDK	Programmatic access to MCPJam for custom tooling, scripting, and integrations. Read more
CI/CD	Run MCPJam checks and evals in GitHub Actions and other CI systems to gate PRs on regressions. Read more

Get help

Discord

Ask the team and the community.

GitHub

File an issue or open a PR.

Changelog

What shipped, and when.

​Four ways to get started