faf-server-card-ref

A reference MCP Server Card that carries FAF context in _meta — proven conformant, served live.

One Cloudflare Worker is, simultaneously:

1. An MCP Catalog (discovery entrypoint) at /.well-known/mcp/catalog.json,
2. A conformant MCP Server Card at /mcp/server-card — the reserved default location (#22), served as application/mcp-server-card+json; /.well-known/mcp/server-card kept for back-compat, and
3. A live minimal MCP endpoint at /mcp (the protocol layer),

— the card and the runtime both carry FAF context in the reverse-DNS _meta slot (one.faf/context). Discovery and protocol say the same thing, so the card never contradicts the running server (#23).

This is a show-the-flow artifact, not a pitch. It demonstrates — with receipts you can curl — that FAF is a well-behaved citizen of MCP's own _meta extension mechanism: the context layer, registered and live.

Cast-iron: conformance is proven, not asserted

npm install
npm test          # WJTTC: Brake · Engine · Aero · Tyres

The suite validates the card against MCP's own published schema (schema/server-card.schema.json, JSON Schema 2020-12, vendored from experimental-ext-server-card) and drives the Worker's fetch handler directly. Green = a conformant Server Card. Tyres (live probes) grey-skip unless WJTTC_TARGET is set.

Receipts (after npm run deploy)

# Discovery — the Catalog entrypoint
curl https://context.faf.one/.well-known/mcp/catalog.json

# The Server Card — reserved default location, application/mcp-server-card+json
curl -H 'accept: application/mcp-server-card+json' https://context.faf.one/mcp/server-card

# The FAF context the card's _meta.faf points to (self-hosted, application/vnd.faf+yaml)
curl https://context.faf.one/.well-known/project.faf

# Protocol — same FAF context in _meta (#23)
curl -s https://context.faf.one/mcp -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-11-25"}}'

The _meta shape

"_meta": {
  "one.faf/context": {
    "faf": "https://context.faf.one/.well-known/project.faf",  // self-hosted pointer to the .faf context (host-derived)
    "mediaType": "application/vnd.faf+yaml",             // IANA-registered media type
    "iana": "https://www.iana.org/assignments/media-types/application/vnd.faf+yaml",
    "deterministic": true,                               // the score is mechanical + reproducible
    "scoreEndpoint": "https://faf.one",                  // where the live score is computed (we don't bake a number)
    "generated": "<ISO-8601>"
  }
}

Deliberate honesty (FAF doctrine)

• No baked score. The card points to where the deterministic score is computed rather than asserting a value that could go stale. FAF don't lie.
• Only advertises protocol 2025-11-25 — what /mcp genuinely answers. No claimed RC support we don't implement. Honest-first. (Add 2026-07-28 when /mcp truly speaks it.)
• remotes[].url is derived from the request host, so the card is truthful wherever it's deployed.

Layout

src/card.js          card + catalog + the FAF context block (source of truth)
src/index.js         the Worker (catalog + card + minimal MCP + landing)
src/projectfaf.js    the served project.faf string (drift-guarded vs ./project.faf)
project.faf          the repo's own FAF context (app_type: server-card, TROPHY 100%)
schema/              MCP's own server-card.schema.json (vendored)
test/                WJTTC suite — Brake / Engine / Aero / Tyres
examples/            generated conformant snapshot

Why this exists

FAF is the C in MCP — Model (any) · Context (FAF) · Protocol (any). MCP's discovery layer (Server Cards) deliberately carries identity + transport and excludes deeper context. That exclusion is exactly the slot FAF fills. This repo is the running proof that it fits — as a good citizen of MCP's own conventions, not a competing format.