allfeatures

allfeatures is a showroom for the MCP protocol itself. Rather than doing one job well, it exercises the moving parts a client and server need to agree on: plain text results, images, annotations, embedded resources, resource links, structured content, a long-running call, and the three features that only work when the connected client helps out — sampling, roots and elicitation. If you are building a client, point it at allfeatures and watch each feature light up (or fail honestly, with a clear error, when your client does not offer it).

Install

npx @reneturcios/allfeatures echo hello

Or run the container image:

docker run -i ghcr.io/cloudcorprecords/allfeatures

The container defaults to the MCP server (see below). Pass CLI arguments to use it as a CLI instead.

CLI

Only the two tools that make sense without a client are exposed as commands:

allfeatures echo hello there   # hello there
allfeatures add 2 3            # 5
allfeatures add -1.5 0.5       # -1
allfeatures --version          # 0.1.0

Exit codes: 0 on success, 1 when the arguments cannot be handled (for example, add given non-numeric input), 2 for usage errors.

MCP server

One bin serves both faces. The mcp subcommand starts a stdio MCP server:

npx -y @reneturcios/allfeatures mcp

MCP client configuration:

{
  "mcpServers": {
    "allfeatures": {
      "command": "npx",
      "args": ["-y", "@reneturcios/allfeatures", "mcp"]
    }
  }
}

Tools

| Tool | Input | What it returns | | --- | --- | --- | | echo | message (string, required) | The message, unchanged, as text. | | add | a, b (numbers, required) | The sum, as text. | | longRunningOperation | duration (number, optional, seconds, default 10), steps (number, optional, default 5) | Waits the duration split across the steps, then a completion note. | | printEnv | — | The server process environment as JSON text. | | sampleLLM | prompt (string, required), maxTokens (number, optional) | A completion sampled from the client's model (see below). | | getTinyImage | — | A 1x1 transparent PNG as image content, plus a short text note. | | annotatedMessage | messageType ("error" / "success" / "debug", required), includeImage (boolean, optional) | A text message whose annotations (audience and priority) depend on the type; the tiny image is attached when includeImage is true. Errors are priority 1 for user and assistant, successes are priority 0.7 for the user, debug notes are priority 0.3 for the assistant. | | getResourceReference | resourceId (number, required) | An embedded text resource with URI demo://resource/<resourceId>. | | getResourceLinks | count (number, required, 1–10) | That many resource_link items. Counts outside 1–10 are an error. | | structuredContent | location (string, required) | Fixed sample weather (72°F, Sunny, 45% humidity) for the location, as structuredContent with matching JSON text alongside. | | listRoots | — | The client's roots, as JSON text (see below). | | startElicitation | — | The outcome of asking the user for a short response (see below). | | zip | — | An embedded blob resource (application/zip) holding a real, minimal ZIP archive with one stored file, hello.txt. The archive is assembled byte by byte — CRC32, local header, central directory — with no archive library. |

Client-capability tools

sampleLLM, listRoots and startElicitation cannot be answered by the server alone: they ask the connected client to do something (sample its model, list its roots, prompt its user). allfeatures only sends those requests when the client advertised the matching capability during initialisation. When it did not, the tool returns an error result saying exactly that — the server never invents a plausible-looking answer.

Development

npm install
npm run build   # tsc -> dist/
npm test        # node test runner over test/*.test.ts, no network
npm run dev     # run the CLI from source via tsx

License

MIT — see LICENSE.