Commerce & Payments · Integration
Square
Add Square to your product for your customers, and give your AI agents governed access to it.
Square is the point of sale and the payment processor at once, which makes location the object an embedded Square integration has to respect: catalog, inventory counts, staff and takings are all scoped by location, and a report that ignores that gives a multi-site merchant the wrong number. Payments, orders, the catalog behind them, customers and invoices are read and written per merchant, and a refund is its own record rather than an edit to a payment. Writes carry an idempotency key, because taking a card payment twice is not a mistake a merchant forgives. Each merchant authorises their own account and grants only the permissions your features use, and fastn keeps the tokens, the webhook subscriptions and the API version upkeep on its side.
In your product
Embedded for your customers. Per-tenant auth, no per-customer code, maintained by fastn.
Let each merchant connect their own Square account so your product takes payments and reads takings without ever holding card data.
Read and write catalog items and their variations per location, so your product shows what that site actually sells.
Create an invoice or an order from your product and let Square collect on it, with an idempotency key so a retry cannot charge twice.
Subscribe to payment, refund and order webhooks so fulfilment or accounting runs the moment money moves.
For your AI agents
Governed, audited access for the agents you build, through the MCP server.
An agent reports a location's takings and refunds for a period and explains which items drove the change.
An agent issues an approved refund within scoped permissions, idempotently, with the transaction recorded.
An agent looks up a buyer's payment history before answering a dispute question.
Example prompt
Compare last week's takings by location in Square and tell me which items sold worse than the week before.
Set up Square in 4 steps
- 01Enable the Square connector in your fastn dashboard.
- 02Have each merchant authorise their own Square account, granting only the payment, catalog and customer permissions your features use.
- 03Map the locations, catalog items and customer fields your product uses, then subscribe to the payment and order webhooks you need.
- 04Call it from your product and expose the same connection to your agents through the MCP gateway.
Why teams use the Square integration
What you get by embedding it with fastn instead of building it yourself.
- Ship a Square integration without building it. Your customers connect their own Square account inside your product and work their orders, payments and customers there, with no per-customer code on your side.
- Handle the part that actually costs time: money and order state must never be double-applied, and reconciliation has to be possible. fastn owns the auth, token refresh, rate limits, pagination and breaking-change fixes, so a Square update is not your on-call problem.
- One integration serves your product and your agents. The same governed Square connection powers in-product features and gives AI agents scoped, audited access, so you keep commerce and payment records in step with your product without wiring it twice.
Used by these teams
Compare with
Stripe
Clover
ShopifyOften used alongside
Tools the same teams tend to run next to Square, across other categories.
NetSuite
Notion
Box
DocusignSquare integration FAQ
How do I add a Square integration to my product?
Enable the Square connector in your fastn dashboard, then let each customer authenticate their own Square account. fastn handles the OAuth flow, token storage and refresh per tenant, so there is no Square client code in your app and no per-customer branch in your codebase. Setup is 4 steps.
Do my customers each connect their own Square account?
Yes. Every connection is scoped to the individual customer, so each authorises their own Square account and only ever sees their own orders, payments and customers. That per-tenant isolation is the point of an embedded integration: you support the long tail of customer setups without maintaining an integration per customer.
Can AI agents use this Square integration?
Yes. The same connection is exposed to your agents through the fastn MCP gateway, with permissions scoped per tenant and every call audited. An agent reports a location's takings and refunds for a period and explains which items drove the change.
Who maintains the Square integration?
fastn does. When Square changes an endpoint, deprecates a field or alters its auth, the fix lands in the connector rather than in your backlog, and your customers' connections keep working.
Is the Square integration safe for payment and order writes?
Writes are idempotent, so a retry cannot double-charge or duplicate an order, and every call is logged per tenant so a transaction can be reconciled against the event that triggered it.
Can my product react to a new order, payment or refund immediately?
Yes, through event triggers, so fulfilment, entitlement or accounting steps run as soon as the event lands rather than on a nightly sync.
What can I build with the Square integration?
A common starting point: let each merchant connect their own Square account so your product takes payments and reads takings without ever holding card data. Teams also use it for the other use cases listed above, and expose it to agents for governed reads and writes.
How much does the Square integration cost?
It is included. Pricing is based on connected accounts, not on how many connectors you enable, so adding Square does not change your per-connector cost. You can start free with 3 connected accounts.
Add Square to your product
Start free with 3 connected accounts. No sales call required, and no per-customer integration code.