OpenMCP Client CLI
The openmcp CLI and a VS Code extension for debugging MCP servers: tools, prompts and resources, chat with a model, test cases
- 750 ★ on the repository
- Last commit
- Apache-2.0
Extended access
Why this level
- The tool launches local MCP server processes and calls their tools with your user's permissions
- For model-based testing, prompts and tool outputs go to the chosen provider, and its API key is required
Install
- Works in
In your terminal, with SkillFoxx CLI
npx skillfoxx add cli/openmcp-clientDetects the agents on your machine, shows the access level and pins the version.
Other ways to install
Access and checks
How we reviewExtended accessThe tool runs code or makes network calls and only reads external data.
- The tool launches local MCP server processes and calls their tools with your user's permissions
- For model-based testing, prompts and tool outputs go to the chosen provider, and its API key is required
This is third-party code. Review the repository files before installing.
What it does
OpenMCP combines an MCP server inspector and a chat client in one tool. You connect a server, test its tools, prompts and resources, then move the verified tools to the interactive testing section and run them through a language model. DeepSeek, OpenAI, Qwen, Gemini, Grok, Mistral, MiniMax, Groq, Perplexity, Kimi, Ollama, OpenRouter and any OpenAI-compatible server are supported. You can debug several MCP servers at once and save debugging results. The tool installs as an extension for VS Code, Trae and Cursor. For the terminal there is the `openmcp` CLI from the npm package `@agent-ruler/openmcp`: `openmcp gateway start` brings up a gateway on `ws://localhost:8282`, and the `mcp`, `debug`, `setting` and `skills` command groups manage server configuration, tool calls and model settings. `openmcp start` opens the web UI. The repository also ships the `agent-ruler-openmcp` skill, which teaches an agent to install the package, start the gateway, diagnose the setup and use the CLI commands. When debugging is done, the `openmcp-sdk` package turns the verified set of servers and prompts into an agent app in TypeScript.
Who it is for. For MCP server authors and anyone wiring up third-party servers who needs to check tools and prompts by hand and through a model before handing the server to an agent.
Good fit when
- You write an MCP server and want to call its tools with different arguments without launching an agent
- You need to confirm a language model picks the right tool and fills parameters correctly, and compare several models
- A script or CI job must run `openmcp debug tool call` and check the server's reply
- An agent should install `openmcp`, start the gateway and show logs itself when startup fails
- A debugged set of servers and prompts has to be deployed as a ready TypeScript agent through `openmcp-sdk`
Not a fit when
- You only need the official minimal protocol inspector: OpenMCP has more features, including chat and project management
- You work without Node.js 18 or newer: the CLI and gateway will not start
- You need a guard against dangerous operations: there is no confirmation before risky calls yet, and the roadmap item is still open
- You need to update a connected MCP server without a restart: hot update is not available yet
Example request
Connect my MCP server from mcp-server.json through openmcp and call the echo tool with message=hi.Limitations
The CLI needs Node.js 18 or newer, and most commands require a running gateway, on port 8282 by default. With another port, add `-g ws://127.0.0.1:9000` to commands. The documentation and some guides are in Chinese.
The extension ships for VS Code, Trae and Cursor, and other editors get the CLI and the `openmcp start` web interface. Models with a custom protocol are not connected yet, and testing through a model needs an API key from the chosen provider. The repository was last updated on 4 June 2026.
How to disable. Stop the gateway with `openmcp gateway stop` and remove the package with `npm uninstall -g @agent-ruler/openmcp`. The extension is disabled in the extension list of VS Code, Trae or Cursor.
FAQ
How do I install OpenMCP from npm?
Run `npm install -g @agent-ruler/openmcp` and check `openmcp --version`. Then start the gateway with `openmcp gateway start`, since most commands work only with it.
How do I add an MCP server and call its tool with `openmcp`?
Add the server from a file with `openmcp mcp server add --file ./mcp-server.json`, connect with `openmcp mcp session connect --id <serverId>`, then call the tool: `openmcp debug tool call --name echo --args "{\"message\":\"hi\"}"`.
Which models can OpenMCP use to test tools?
DeepSeek, OpenAI, Qwen, Gemini, Grok, Mistral, MiniMax, Groq, Perplexity, Kimi, Ollama, OpenRouter and any OpenAI-compatible server.
What if the `openmcp gateway` does not start?
Run the gateway in the foreground with `openmcp gateway run -p 8282` to see output in the terminal, then read the logs: `openmcp gateway logs -n 200` shows `gateway.log` and `gateway-startup.log`, and `openmcp gateway logs-dir` names the folder.
How is OpenMCP different from MCP Inspector?
MCP Inspector checks a server's protocol. OpenMCP adds a chat with a language model, project management, debugging several servers at once, saved results and a CLI for scripts.
Discussion
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README in short
Screenshots and a video show the extension at work: the inspector, resources, chat, project management, model selection and XML mode. An `openmcp-sdk` agent deployment example and a roadmap table with completion percentages follow. The CLI has its own description with examples and links to the command reference.