@crossly/buyer-mcp

Model Context Protocol server for the Crossly Buyer API — lets an AI agent act on a person's own shopping.

Not on npm yet. @crossly/buyer-mcp is unreleased — the command below will 404 until the first publish. To try it now, clone this repo and build from source. Star or watch to hear when it lands.

npx -y @crossly/buyer-mcp

This is not the seller server

@crossly/mcp drives a seller's store — listings, crossposting, fulfilment. This drives a shopper's account — cart, orders, wishlists, offers, cashback.

Different API, different principal, different token. Run both in one host if you like; they read different env vars precisely so that works.

Related MCP server: mcp-amazon

Nothing here spends money

No tool completes a purchase and no endpoint sits behind one. quote_my_cart prices a basket; offer_on_listing proposes a number a seller may accept, after which the person still completes checkout themselves.

An agent must never tell a user it has bought something.

Configure

Claude Desktop (claude_desktop_config.json), Cursor, Cline — same shape everywhere:

{
  "mcpServers": {
    "crossly-buyer": {
      "command": "npx",
      "args": ["-y", "@crossly/buyer-mcp"],
      "env": {
        "CROSSLY_BUYER_TOKEN": "crossly_oat_..."
      }
    }
  }
}

CROSSLY_BUYER_TOKEN is a buyer OAuth token carrying buyer:* scopes, obtained by sending the shopper through the Crossly consent screen. There is no buyer equivalent of a personal access token, because these scopes are granted by a person agreeing to them.

Hand it a seller crossly_pat_… and it refuses at startup with a message saying which token it wanted — rather than a 403 on the agent's first tool call, which reads as a broken tool.

Tools (15)

Scopes are enforced server-side

A token without buyer:cashback:read simply cannot call get_my_cashback — the tool returns the API's refusal rather than pretending. Cashback is deliberately a separate grant from orders: an app that reads what you bought has no automatic business knowing what you earned.

Two notes for agents

Money is always cents. amountCents, totalCents, bucksBalanceCents. Never present the raw integer as dollars.

A cart quote is a floor. taxComplete: false means no delivery address is known, so shipping and tax are incomplete. Say so rather than quoting the total as final.

Also available

• @crossly/buyer-sdk — TypeScript client

• @crossly/buyer-cli — crossly-buyer on the command line

License

MIT