inspector: Test and Debug MCP Servers and Apps

Overview

MCPJam Inspector is a testing and evaluation platform for developers building MCP servers, MCP apps, and ChatGPT apps. It brings server interactions, client behavior, protocol traces, and model-driven tests into one workflow, helping identify integration differences and failures before deployment.

It is useful both for hands-on local debugging and repeatable checks in automated pipelines. The project provides a hosted app, desktop app, terminal interface, and SDK, with local options for connecting to HTTP/S and STDIO servers.

Key Features

• Inspect and invoke tools, resources, resource templates, prompts, and elicitation flows with JSON-RPC logs.
• Exercise servers through a chat playground with trace and raw views, including support for MCP app and OpenAI Apps SDK interfaces.
• Debug OAuth flows and run guided protocol conformance checks.
• Define test cases with expected tool calls, run evaluations across models, and track accuracy over time.
• Compare behavior across client configurations and inspect traces of agent steps and tool calls.
• Use a CLI and SDK for server checks, scripted inspection, and CI/CD workflows.
• Share server configurations through team workspaces with real-time sync.

Use Cases

• An MCP server developer can reproduce a tool or resource failure and inspect the underlying JSON-RPC messages during local development.
• A team integrating with multiple AI clients can compare behavior across client configurations before releasing an integration.
• An engineer responsible for authentication can diagnose OAuth errors and check conformance to supported protocol versions.
• A team can run evaluation cases and conformance checks in CI to catch behavior changes before merging or deploying.

Project Facts

• Language: TypeScript
• License: NOASSERTION
• Stars: 2.2k
• Forks: 293
• Topics: anthropic, chatgpt, cicd, debugger, evals, evaluation, inspector, mcp, mcp-apps, mcp-clients, mcp-inspector, mcp-server, mcp-tools, modelcontextprotocol, oauth, oauth2, openai, openai-apps-sdk, opensource, tracing
• Archived: no

Getting Started

Run the local terminal version with Node.js 20 or later:

npx @mcpjam/inspector@latest

Alternatively, open the hosted app. See the repository README for desktop, Docker, and configuration details.

Alternatives

• promptfoo: Promptfoo evaluates prompts and LLM applications, including security checks, while Inspector focuses on testing MCP servers and apps across clients and models.

Considerations

The hosted app supports HTTPS server URLs only. Local STDIO connections and some local workflows require the terminal or desktop app. The terminal install requires Node.js 20 or later. The repository metadata reports the license as NOASSERTION, while the README states that the project is licensed under Apache License 2.0. The project is active and has a substantial open issue count, so check the issue tracker for current reports relevant to your setup.