Everything MCP: a test server that exercises the whole protocol

If you build MCP clients, gateways or debugging tools, the hard part is finding a peer that exercises every corner of the protocol. Ordinary servers only use tool calls, so sampling, elicitation and resource subscriptions go untested. Everything is the official answer. Its README says up front that it isn’t meant to be useful; it’s a test server for client builders.

What it does

• Every kind of tool result: simple calls like echo and get-sum, an image from get-tiny-image, structured output with an outputSchema from get-structured-content, and resource links from get-resource-links.
• Server-to-client requests: trigger-sampling-request asks the client to call its LLM and trigger-elicitation-request sends a form-style elicitation, with URL-mode and async task variants too.
• Long jobs and notifications: trigger-long-running-operation simulates a multi-step job with progress notifications, toggle-simulated-logging emits logs at every level, and toggle-subscriber-updates pushes updates for subscribed resources.
• Prompts and resources: prompts with arguments, auto-completion and embedded resources, plus dynamic text, blob and session-scoped resource templates.

Who it’s for

• Engineers building MCP clients, IDE extensions or gateways who need to check protocol coverage.
• People writing MCP tutorials or chasing client compatibility bugs who want a predictable reference server.

Setup

Needs Node.js:

{
  "mcpServers": {
    "everything": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-everything"]
    }
  }
}

There’s also an mcp/everything Docker image.

Our take

It’s here for a different reason than the other entries. Regular users gain nothing from installing it, but for anyone building MCP infrastructure it’s the de facto protocol test bench, and new spec features such as Tasks and URL-mode elicitation often get their first examples here. Compared with writing your own fake server, it covers more and keeps pace with the spec. One warning: get-env returns the server process’s entire environment verbatim, so keep real secrets out of that environment and never wire it into an agent you use day to day. It lives in the MCP servers monorepo, which had about 91k stars as of 2026-10-06; licensing is moving from MIT to Apache-2.0.