Everything MCP Server

npx -y @modelcontextprotocol/server-everything

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

Not a production integration but a test bench: it implements tools, prompts, resources, sampling, elicitation, roots and progress notifications so client authors can see each feature respond. The tool set is deliberately trivial in purpose — echo a string, add two numbers, return a tiny image, run a long operation that reports progress — while the interesting part is the protocol behaviour around them. Some tools only register when the connected client advertises the matching capability. It can be started over stdio, SSE or Streamable HTTP, which makes it the usual target when debugging a new client transport.