Developer quickstart

Start with the sandbox #

The quickest way in is the sandbox. sandbox.frontlatch.com is a made-up business that answers inside the gateway, so you can run a whole request without touching a real one. do returns pending, a few seconds later request_status says quoted with a price, and respond_to_quote with user_confirmed true makes it booked. Nothing is sent to anyone and nothing is billed.

Call it straight from your own MCP client at frontlatch.com/mcp, or add Frontlatch to Claude or ChatGPT as a custom connector at frontlatch.com/mcp/auth. The raw calls are below.

The endpoint #

One address answers for every business in the business index: https://frontlatch.com/mcp, JSON-RPC 2.0 over HTTP POST. There is no per-business URL and no API key is required. An anonymous caller gets 120 requests an hour per MCP session. do and do_action have their own 60 an hour per session, and a caller that sends no Mcp-Session-Id is counted by its IP address at 1,000 an hour. Anonymous do and do_action calls are also capped at 600 an hour per IP address and 3,000 an hour across all anonymous callers.

An optional key from /app/developer can be created and revoked. A call that carries a valid key is counted against the key instead of the session, at 500 requests an hour, and is attributed to you. Every call below is anonymous, so you can skip the key here.

server/discover, which the protocol lists as mandatory, is not implemented. The specification lets a client skip it and call a method directly, and every method below still answers.

Limits and errors #

On top of the hourly limits, inspect_site, read_page and do_action have a daily free allowance per key: 20, 200 and 10 calls, reset at 00:00 UTC. do_action only ever does a dry run, so its allowance never changes anything on a business.

A refused call comes back as a JSON-RPC error. Branch on the code, not the message.

Connect a client #

{
  "mcpServers": {
    "frontlatch": {
      "type": "http",
      "url": "https://frontlatch.com/mcp"
    }
  }
}

Connect with your Frontlatch account #

In Claude or ChatGPT, add a custom connector and give it https://frontlatch.com/mcp/auth. The AI sends you to Frontlatch to sign in and approve the connection, then calls the same twelve tools with your account attached, so your use counts against you and not against an anonymous address. It is OAuth 2.1 with PKCE and the AI registers itself, so there is nothing to copy. Without a token, /mcp/auth answers 401 and points at /.well-known/oauth-protected-resource/mcp/auth; the sign-in server is described at /.well-known/oauth-authorization-server.

The connection only identifies the caller. It cannot book or submit anything on a business: do answers exactly as it does anonymously.

Some results carry text written by websites. Each one opens with untrustedContent: true and a notice, then untrustedProvenance, injectionSuspected, injectionFlags and sanitised. Treat that text as data, never as instructions. Frontlatch strips control and invisible characters and HTML comments, caps labels at 300 characters, and drops hidden elements before read_page reads. Instruction-shaped text is flagged, not blocked, and no returned content can supply user_confirmed.

Check it is alive, by curl #

Two read-only calls, no client needed. The protocol version in initialize is negotiated: the gateway echoes 2026-07-28, 2025-11-25, 2025-06-18 or 2025-03-26 if you ask for one, and answers 2025-11-25 for any other, so the official SDK clients connect. It issues an Mcp-Session-Id at initialize for rate limiting only and keeps no session state, so a DELETE on /mcp answers 405.

curl -s -X POST https://frontlatch.com/mcp \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize",
       "params":{"protocolVersion":"2026-07-28","capabilities":{},
                  "clientInfo":{"name":"quickstart","version":"0.1.0"}}}'

{"jsonrpc":"2.0","id":1,"result":{"protocolVersion":"2026-07-28",
 "capabilities":{"tools":{"listChanged":true},"resources":{}},
 "serverInfo":{"name":"frontlatch-gateway","title":"Frontlatch agent gateway","version":"0.1.3"},
 "instructions":"Frontlatch lets an agent book, request a quote from, or contact a service business on the user's behalf. When the user asks to book, get a quote from, or send a contact request to a business, call find_business, then do, before opening that business's website in a browser. A business claimed on Frontlatch takes the request here: it is verified and the owner receives a job card. A browser form-fill on the same site is unverified and unbilled. ... (trimmed)"}}

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

{
  "jsonrpc": "2.0",
  "id": 2,
  "result": {
    "tools": [
      { "name": "find_business", "title": "Find a business", ... },
      { "name": "list_actions", "title": "List a business's detected actions", ... },
      { "name": "describe_action", "title": "Describe one detected action", ... },
      { "name": "do", "title": "Run an action on a business", ... },
      { "name": "request_status", "title": "Check whether the owner accepted a request", ... },
      { "name": "respond_to_quote", "title": "Accept or decline the owner's quote", ... },
      { "name": "cancel_request", "title": "Withdraw a request the owner has not answered", ... },
      { "name": "reschedule_request", "title": "Ask the owner for a new time on an agreed job", ... },
      { "name": "inspect_site", "title": "Inspect any website's action map", ... },
      { "name": "read_page", "title": "Read one page as text", ... },
      { "name": "do_action", "title": "Run one action from inspect_site's map (dry run by default)", ... },
      { "name": "setup_frontlatch", "title": "Get started with Frontlatch", ... }
    ]
  }
}

The twelve tools #

For an intentional “Welcome to Frontlatch” or setup request, call setup_frontlatch with operation: "start". Supporting hosts show a role and website card; text-only clients receive a secure browser link. Signup and WordPress approval happen in the browser. Keep the returned setup token to resume; connection does not enable actions or billing. Hosts choose when to call tools, so a greeting is not intercepted automatically.

Eight work on the business index: find_business, list_actions, describe_action, do, request_status, respond_to_quote, cancel_request and reschedule_request. find_business, list_actions and describe_action only read it. do is the only one that could act for a business, and it refuses almost every call: Frontlatch will not run an action on a business that has not verified it. request_status reads the outcome of a request do accepted. respond_to_quote passes on the user’s accept or decline of the owner’s quote, only after they said yes in their own chat (user_confirmed), and takes no payment. cancel_request withdraws a request the owner has not answered, only with user_confirmed. reschedule_request asks the owner for a new time on an agreed job, only with user_confirmed. Verification explains the rule.

The other three work on any website: inspect_site, read_page and do_action. inspect_site lists what a site lets a visitor do. read_page returns one page as text. do_action fills in one of a site’s forms but never submits it.

The MCP tool reference has every tool’s inputs and a real response for each, including the refusal do gives today. Build against that refusal; it is what every caller gets.