How does Square keep its tool list small across 40+ services?

It uses three meta-tools — get_service_info, get_type_info, and make_api_request — so the agent discovers a service's methods and parameters and then executes a call, instead of registering a separate tool for every endpoint. Adyen instead exposes discrete tools per operation.

Can I run either in a read-only or test mode?

Yes. Square offers a DISALLOW_WRITES flag for read-only access and a sandbox environment. Adyen recommends starting against its TEST environment and supports a --tools flag to expose only a chosen subset of operations.

Adyen vs Square

Adyen and Square are both payment platforms whose official MCP servers let an agent move real money and manage commerce operations, but they target different ends of the market. Adyen's server exposes its Checkout and Management APIs: on the Checkout side an agent creates payment sessions, retrieves results, lists payment methods, manages payment links, and refunds or cancels authorized payments; on the Management side it administers merchant accounts, point-of-sale terminals, webhooks, payment methods, users, API credentials, and allowed origins — an enterprise, omnichannel posture with deep terminal fleet management. Square's server exposes the entire Connect API through a compact discovery pattern (get_service_info, get_type_info, make_api_request) that reaches 40+ services: payments, checkout and payment links, catalog and inventory, orders, customers, bookings, loyalty, gift cards, refunds, disputes, invoices, subscriptions, and workforce management — the broad commerce surface of a seller-focused platform. Both move money, so both stress scoped credentials and a human in the loop. Here is how they compare.

How they compare

Dimension	Adyen	Square
Market posture	Enterprise and omnichannel: Checkout plus Management APIs, with strong point-of-sale terminal fleet administration (assign terminals, manage apps and certificates, schedule actions).	Seller and SMB commerce: the full Square Connect API spanning payments, catalog, orders, bookings, loyalty, gift cards, invoices, and subscriptions.
API design	Discrete tools per operation — create_payment_session, create_payment_links, refund_payment, list_merchant_accounts, and so on — a direct mapping of Adyen endpoints.	A compact discovery pattern: get_service_info to see methods, get_type_info to learn parameters, then make_api_request to execute — three meta-tools reaching 40+ services.
Breadth of commerce surface	Payments, payment links, refunds/cancels, and rich account/terminal/webhook management — deep on payment processing and merchant operations.	Far broader commerce: alongside payments, it covers catalog, inventory, orders, customers, bookings, loyalty, gift cards, disputes, invoices, subscriptions, and team/workforce.
Deployment and auth	Published as @adyen/mcp, run locally over stdio via npx; pass an Adyen API key and target environment as CLI flags (--env=TEST, --livePrefix for live), with --tools to expose a subset.	Recommended hosted remote at mcp.squareup.com/sse with OAuth and granular scopes, or local stdio via npx with an access token; a DISALLOW_WRITES flag enforces read-only.
Safety guidance	Recommends starting in TEST, scoping the API key to only the APIs the agent needs, and keeping a human in the loop for sensitive actions.	Recommends scoping the token or OAuth grant tightly and offers DISALLOW_WRITES for a safe read-only default against a live merchant account.
Best-fit task	Enterprises that need omnichannel payments and terminal fleet management with precise control over which API surfaces the agent touches.	Sellers on Square that want one agent across the whole commerce stack — payments, catalog, orders, bookings, and more.

Verdict

Both servers let an agent process payments and run commerce operations, so pick by your platform and the breadth you need. Choose Adyen for enterprise, omnichannel payments and serious point-of-sale terminal management, with a tool-by-tool API and CLI flags to scope exactly which surfaces the agent can reach and a TEST-first workflow. Choose Square if you sell on Square and want one agent across the entire commerce stack — payments, catalog, orders, bookings, loyalty, invoices, and subscriptions — reached through its compact discovery pattern, with OAuth scopes and a DISALLOW_WRITES read-only mode. Adyen is the omnichannel processor with terminal depth; Square is the broad seller platform. Either way, because real money moves, scope credentials narrowly and keep a human in the loop.

FAQ

How does Square keep its tool list small across 40+ services?: It uses three meta-tools — get_service_info, get_type_info, and make_api_request — so the agent discovers a service's methods and parameters and then executes a call, instead of registering a separate tool for every endpoint. Adyen instead exposes discrete tools per operation.
Can I run either in a read-only or test mode?: Yes. Square offers a DISALLOW_WRITES flag for read-only access and a sandbox environment. Adyen recommends starting against its TEST environment and supports a --tools flag to expose only a chosen subset of operations.