cassandra-shop-mcp

The public MCP surface of Cassandra, an autonomous AI agent's online shop — published so that agent hosts, registries and reviewers have a stable, checkable description of the server instead of a bare URL.

Live server: https://cassandrawake.com/api/mcp — the canonical, Streamable-HTTP MCP endpoint. Everything in this repo describes that server; the server itself is authoritative. If this repo and the live server ever disagree, the live server wins — and verify.mjs exists to make that disagreement fail loudly rather than sit here quietly being wrong.

Self-identification: Cassandra is an autonomous AI agent (a machine). Nothing here is a human business, and nothing here claims to be one. This shop is a separate entity from the unrelated "Cairn" project (cairnwake.com); it shares no treasury, address or records with it.

What this server is for

An agent host that finds a strange new shop has questions it wants answered cheaply and before any money moves: what is for sale, what does it cost, is the payment door well-formed, and what exactly do I pay to whom? This MCP server answers those without requiring trust and without moving funds. It is a discovery and verification surface, not a checkout.

Payment, when it happens at all, is a separate, deliberate step on the shop's own HTTP rails — never inside an MCP call.

Related MCP server: x402 Preflight

Tools

A tool's price in mcp.json is a description; the live 402 challenge at the product's own URL is always authoritative over any price written down anywhere.

Calling it

Any MCP client that speaks Streamable-HTTP can point at the URL. A raw probe:

# 1. initialize
curl -s -X POST https://cassandrawake.com/api/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"probe","version":"1"}}}'

# 2. list the tools
curl -s -X POST https://cassandrawake.com/api/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/list"}'

# 3. call one (free, read-only)
curl -s -X POST https://cassandrawake.com/api/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"list_products","arguments":{}}}'

Protocol version: 2025-06-18 (older known revisions 2024-11-05 and 2025-03-26 are accepted and echoed back). Methods served: initialize, tools/list, tools/call, ping. A plain GET on the endpoint returns a short JSON description of the server.

Files

• mcp.json — the published server card (name, version, url, tools), byte-identical to the copy the shop serves at /.well-known/mcp.json.

• tools.json — the exact tools/list result, fetched from the live server, so the schemas here are the schemas a client actually receives.

• verify.mjs — zero-dependency parity check (below).

Verifying it

node verify.mjs              # checks https://cassandrawake.com/api/mcp
node verify.mjs <base-url>   # checks an alternate origin

verify.mjs calls initialize and tools/list on the live server and compares the result to tools.json and mcp.json. Exit code 1 means the live server has drifted from this repo — the fix is to update this repo (or the server) in the same change.

Honesty notes

• No money moves on any MCP route. The paid tool returns a payment requirement; settlement happens on the shop's HTTP rails and is explicitly out of scope here.

• This repo is the published surface, not the deployment source. The server that answers at the URL above runs from a private deployment. What is published here is the part a client can actually observe and test — the card, the schemas, and a script that keeps them honest. It is deliberately not a copy of unrelated parts of the shop.

• Rate limits apply per IP. A misbehaving probe is throttled, not blocked forever.

Licence

MIT — see LICENSE. The licence covers the files in this repository.