Menta

Menta by Crossmint is a plugin that lets your AI assistant buy, book and order online, at stores around the world. Tell it what you want and a price limit; a Crossmint browser agent runs the checkout at the store, asks you when the store needs an answer, and stops for your approval before any payment. Payments are approved only by you, in Crossmint's UI. The model never can. Menta is open source and a working showcase of Crossmint Agent Checkouts and Agent Cards.

Hosted at menta.crossmint.com.

Where it runs

• Web app: after sign-in, /home (connecting an agent first; then recent activity, connected agents and what's left to set up; on phones, the app's menu), /activity (every purchase, from any assistant), /wallet (saved cards, each with its name, default, security code and the spending limits on it), /spending-limits (the spending limits, or order intents, the user's cards have paid under; a user can make one there, or from a card's details, with an amount, a name, an optional store and when it expires) and /settings (account, delivery addresses, agents, store sign-ins, notifications, language, and deleting the account, each section on its own page). /install redirects to /home; /transactions, /addresses and /connections redirect to their new pages. Translated into 16 languages (apps/web/lib/i18n).
• Web chat at /chat: a place to try Menta's own agent, built on Eve, with a checkout dock above the composer.
• ChatGPT and Claude: an MCP server at /mcp (OAuth via Stytch). The host's model finds the item; Menta buys it. Hosts that support MCP Apps show Menta's checkout card inline when the user must act (a store question, private details, a spending limit for the payment) and for the receipt; for a checkout in progress, the user asks the assistant.
• Grok Bot, Codex, Claude Code, Cursor and other MCP clients: the same MCP server, with text results, native forms where the client supports them, and a link to Menta's secure page for payment.
• Plugin: plugins/menta packages the MCP server with setup and buy skills for ChatGPT, Codex, Claude, Cursor and Grok Bot.

/ is the public homepage, with one URL per language (/es, /ja…). docs/HOSTS.md covers what each host supports.

Goals and non-goals

Goals:

• Delegate a real checkout from any assistant and finish it with the user in the loop: store questions, private details and payment approval.
• The same user, cards, addresses and memory on every surface. The web and MCP paths resolve to one Stytch user, which is the Crossmint user.
• Two reusable Eve extensions for Agent Checkouts and Agent Cards that other agents can mount on their own.

Non-goals:

• Our own order ledger, spending rules, checkout state machine or job runner. Crossmint is the source of truth for checkouts, cards, payment authority and purchase history.
• Competing with general assistants. Conversation quality comes from the model; Menta adds the ability to buy.

How it uses Crossmint

• Agent Checkouts runs each checkout: a browser agent opens the store, shops and checks out, never spending above the limit. Menta starts, reads, answers, steers and cancels runs; it keeps no checkout state of its own.
• Agent Cards saves the user's cards. Card entry is Crossmint's own form (CrossmintPaymentMethodManagement); Menta only ever sees a card's brand, last four and expiry.
• Spending limits (Crossmint order intents) carry payment approval. The user picks a card and approves a limit in Crossmint's UI (with verification or CVC when the card rail asks). When a checkout asks for a card payment, the user's assistant picks the limit that fits what the purchase is for and Menta pays with it after checking it covers the payment (packages/agent/src/limit-payments.ts); with none that fits, the assistant asks for a generic one or the user approves one there, and its orderIntentId goes to the run. An assistant can also ask for a limit ahead of time (request_spending_limit): the user approves it on a Menta page whose link is sealed for them and works for 24 hours. The card network's check runs on the limit being approved; if it fails, the limit pays with Crossmint's encrypted card.
• Protected inputs handle store passwords and codes. Crossmint's CrossmintProtectedInput returns a reference, never the value.
• Crossmint trusts Stytch session JWTs, so browser components act as the signed-in user.

Security model

• The model can't approve, create or raise a spending limit, or pick one to pay with. Approval happens only in Crossmint's UI inside Menta's signed-in surfaces (the web chat dock, the secure page /checkouts/[runId], or the in-host card), through paths no model tool can call.
• Card numbers, CVCs, passwords and verification codes never pass through chat, tools or logs.
• Capability URLs (such as a checkout's live view) and credentials stay out of model context.
• The user is always derived from the verified session or OAuth token, never from tool arguments.

See SECURITY.md to report a vulnerability.

Prerequisites

• Node 24.15 and pnpm 10.34.
• A Crossmint production project (Agent Checkouts is production-only) with a server key, a client key, and JWT authentication set to trust your Stytch project.
• A Stytch Consumer project for login, with Connected Apps enabled for MCP clients.
• Neon Postgres (the app uses Neon's serverless driver), as DATABASE_URL.
• Vercel AI Gateway for the model.

docs/CREDENTIALS.md lists every variable and the dashboard settings.

Quick start

pnpm install
cp apps/web/.env.example apps/web/.env.local   # fill it in, see docs/CREDENTIALS.md
pnpm db:migrate
pnpm dev

Open http://localhost:3000 for the homepage and http://localhost:3000/chat for the chat. With a Stytch test project you can sign in as sandbox@stytch.com with code 000000. Local MCP clients connect to http://localhost:3000/mcp.

Checkouts are real: they run against live stores. Cancel a run before payment if you're only trying it out.

Deploying to Vercel

1. Import the repo with apps/web as the root directory. Its vercel-build script runs the database migrations, then builds.
2. Set the environment variables from apps/web/.env.example, with OCA_WEB_ORIGIN set to the deployment's exact origin. On Vercel the AI Gateway can use OIDC instead of AI_GATEWAY_API_KEY.
3. Add the origin in Stytch (redirect URLs, Connected Apps authorization URL {origin}/oauth/authorize) and in Crossmint (the client key's authorized origins).

Details for each step are in docs/CREDENTIALS.md.

Forking

The official plugin in plugins/menta points at https://menta.crossmint.com. For your own deployment, change PRODUCTION_ORIGIN in apps/web/lib/site.ts to your origin and run pnpm plugin:sync so the plugin files point at your server. Forks may not present themselves as Crossmint or Menta by Crossmint; see NOTICE.

Project layout

apps/web/                          Next.js app: homepage, chat, secure checkout page, settings, MCP server route, OAuth consent
packages/agent/                    the Eve agent, MCP server, in-host checkout card and shared checkout UI
packages/crossmint-agent-checkouts/  reusable Eve extension for Crossmint Agent Checkouts
packages/crossmint-agent-cards/      reusable Eve extension for Crossmint Agent Cards
plugins/menta/                       installable plugin for ChatGPT, Codex, Claude, Cursor and Grok Bot
migrations/                        Neon Postgres migrations (run by pnpm db:migrate)
scripts/                           dev server, migrations and plugin sync
docs/                              design and setup docs

Commands

Command	What it does
pnpm dev	Builds the packages and runs the web app and agent at http://localhost:3000
pnpm verify	Biome lint and format check, package builds, TypeScript
pnpm test	Vitest unit and contract tests
pnpm build	Production build of the web app
pnpm db:migrate	Applies migrations/ to DATABASE_URL
pnpm plugin:sync	Regenerates the plugin files in plugins/menta
pnpm card:fixtures	Serves the MCP server over fake checkouts in every state, for testing the in-host card

Docs

• docs/EDD.md: architecture and request flows.
• docs/HOSTS.md: what each assistant host supports and how Menta behaves there.
• docs/ADDRESSES.md: how saved addresses work in checkouts.
• docs/CREDENTIALS.md: configuration and provider setup.
• plugins/menta/README.md: installing the plugin locally.
• CONTRIBUTING.md, SECURITY.md, CODE_OF_CONDUCT.md.

License

Apache-2.0. Third-party notices and trademarks are in NOTICE.