Square

square-rest-v2restprimary

98% coverage

Offload Valuejudged · weight 15 · Oct 5, 2026

Square's API performs real-world irreversible side effects an agent cannot simulate: capturing card payments, issuing refunds, managing chargebacks/disputes, payouts to bank accounts, publishing invoices, terminal checkouts, and gift card/loyalty balance mutations. It also holds proprietary seller data (catalog, inventory, payouts, customer profiles) and handles PCI-sensitive card-on-file storage. None of this is approximable through inference.

• https://developer.squareup.com/reference/square

  Take payments, process refunds, manage disputes, enable subscriptions, and get paid for your sales.

• https://developer.squareup.com/reference/square

  Payments Take payments, process refunds, manage disputes, enable subscriptions, and get paid for your sales.

• https://developer.squareup.com/reference/square

  Take payments, process refunds, manage disputes, enable subscriptions, and get paid for your sales.

Interaction Costmeasured · weight 15 · Oct 5, 2026

Median over 2 successful run(s): 11911.5 tokens, 3.5 calls. Ratio to the best in "payments" (3 surfaces measured, v0.2 scale). Cold, without documentation: 1/1 succeeded.

Error Recoverabilityprobed · weight 15 · Oct 5, 2026

unknown_endpoint → HTTP 404, clarity 75/100 (field named: yes, allowed values: yes, RFC 9457: no) · wrong_type → HTTP 400, clarity 75/100 (field named: yes, allowed values: yes, RFC 9457: no) · hallucinated_enum → HTTP 400, clarity 75/100 (field named: yes, allowed values: yes, RFC 9457: no) · unknown_field → HTTP 200, clarity 30/100 (field named: no, allowed values: no, RFC 9457: no) · missing_required_param → HTTP 400, clarity 50/100 (field named: no, allowed values: yes, RFC 9457: no) · idempotency_replay → HTTP 200, clarity 30/100 (field named: no, allowed values: no, RFC 9457: no)

• https://connect.squareupsandbox.com/v2/customers

  HTTP 401: { "errors": [ { "category": "AUTHENTICATION_ERROR", "code": "UNAUTHORIZED", "detail": "This request could not be authorized." } ] }

• https://connect.squareupsandbox.com/v2/customers/nonexistent_resource_xyz

  HTTP 404: {"errors": [{"code": "NOT_FOUND","detail": "Customer with ID `nonexistent_resource_xyz` not found.","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?limit=not_a_number

  HTTP 400: {"errors": [{"code": "EXPECTED_INTEGER","detail": "Expected an integer value.","field": "limit","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?sort_field=nonexistent

  HTTP 400: {"errors": [{"code": "INVALID_ENUM_VALUE","detail": "`nonexistent` is not a valid enum value for `sort_field`.","field": "sort_field","category": "INVALID_REQUEST_ERROR"}]}

Doc Legibilitymeasured · weight 12 · Oct 5, 2026

text/markup ratio 5.4% (weight 30) · rendering without JavaScript undetermined (excluded from the calculation) (weight 25) · machine-readable spec: none found (weight 25) · llms.txt: https://developer.squareup.com/llms.txt (weight 10) · 0 runnable example(s) (weight 10). Weighted average over 75 points of available sub-criteria.

• https://developer.squareup.com/reference/square
• https://developer.squareup.com/llms.txt

Auth Frictionmeasured · weight 10 · Oct 5, 2026

Authorization: Bearer <key>, verified by a successful call. One header, no ceremony.

• https://connect.squareupsandbox.com/v2/customers

  HTTP 401: { "errors": [ { "category": "AUTHENTICATION_ERROR", "code": "UNAUTHORIZED", "detail": "This request could not be authorized." } ] }

• https://connect.squareupsandbox.com/v2/customers/nonexistent_resource_xyz

  HTTP 404: {"errors": [{"code": "NOT_FOUND","detail": "Customer with ID `nonexistent_resource_xyz` not found.","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?limit=not_a_number

  HTTP 400: {"errors": [{"code": "EXPECTED_INTEGER","detail": "Expected an integer value.","field": "limit","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?sort_field=nonexistent

  HTTP 400: {"errors": [{"code": "INVALID_ENUM_VALUE","detail": "`nonexistent` is not a valid enum value for `sort_field`.","field": "sort_field","category": "INVALID_REQUEST_ERROR"}]}

Safety & Reversibilityprobed · weight 10 · Oct 5, 2026

Two identical POSTs with the same idempotency key in the body return the same resource (N6HGYAYF6PTARQERCT78ZEQ344). An agent can retry without risking a duplicate. (weight 35) · Isolated test environment available. (weight 25). Weighted average over 60 points of measured sub-criteria.

• https://connect.squareupsandbox.com/v2/customers

  HTTP 401: { "errors": [ { "category": "AUTHENTICATION_ERROR", "code": "UNAUTHORIZED", "detail": "This request could not be authorized." } ] }

• https://connect.squareupsandbox.com/v2/customers/nonexistent_resource_xyz

  HTTP 404: {"errors": [{"code": "NOT_FOUND","detail": "Customer with ID `nonexistent_resource_xyz` not found.","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?limit=not_a_number

  HTTP 400: {"errors": [{"code": "EXPECTED_INTEGER","detail": "Expected an integer value.","field": "limit","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?sort_field=nonexistent

  HTTP 400: {"errors": [{"code": "INVALID_ENUM_VALUE","detail": "`nonexistent` is not a valid enum value for `sort_field`.","field": "sort_field","category": "INVALID_REQUEST_ERROR"}]}

Payload Efficiencyprobed · weight 8 · Oct 5, 2026

No discoverable field selection (tested fields, select, _fields, expand, properties): the agent swallows the whole resource. (weight 35) · No cursor pagination marker in the response. (weight 20) · Nested envelope or non-list shape. (weight 10) · No ETag. (Compression is not measurable: the runtime decompresses it and strips the header.) (weight 10). Weighted average over 75 points of measured sub-criteria.

• https://connect.squareupsandbox.com/v2/customers

  HTTP 401: { "errors": [ { "category": "AUTHENTICATION_ERROR", "code": "UNAUTHORIZED", "detail": "This request could not be authorized." } ] }

• https://connect.squareupsandbox.com/v2/customers/nonexistent_resource_xyz

  HTTP 404: {"errors": [{"code": "NOT_FOUND","detail": "Customer with ID `nonexistent_resource_xyz` not found.","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?limit=not_a_number

  HTTP 400: {"errors": [{"code": "EXPECTED_INTEGER","detail": "Expected an integer value.","field": "limit","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?sort_field=nonexistent

  HTTP 400: {"errors": [{"code": "INVALID_ENUM_VALUE","detail": "`nonexistent` is not a valid enum value for `sort_field`.","field": "sort_field","category": "INVALID_REQUEST_ERROR"}]}

Task Atomicitymeasured · weight 6 · Oct 5, 2026

Median over 2 successful run(s): 11911.5 tokens, 3.5 calls. Ratio to the best in "payments" (3 surfaces measured, v0.2 scale). Cold, without documentation: 1/1 succeeded.

Prior Knowledge Coveragemeasured · weight 5 · Oct 5, 2026

Median over 2 successful run(s): 11911.5 tokens, 3.5 calls. Ratio to the best in "payments" (3 surfaces measured, v0.2 scale). Cold, without documentation: 1/1 succeeded.

Async Compatibilityprobed · weight 2 · Oct 5, 2026

POST /customers returns an identifier, and GET /customers/{id} reads it back (HTTP 200): the result can be retrieved by polling, with no server to host. Long-polling / SSE not probed, excluded from the weighting.

• https://connect.squareupsandbox.com/v2/customers

  HTTP 401: { "errors": [ { "category": "AUTHENTICATION_ERROR", "code": "UNAUTHORIZED", "detail": "This request could not be authorized." } ] }

• https://connect.squareupsandbox.com/v2/customers/nonexistent_resource_xyz

  HTTP 404: {"errors": [{"code": "NOT_FOUND","detail": "Customer with ID `nonexistent_resource_xyz` not found.","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?limit=not_a_number

  HTTP 400: {"errors": [{"code": "EXPECTED_INTEGER","detail": "Expected an integer value.","field": "limit","category": "INVALID_REQUEST_ERROR"}]}

• https://connect.squareupsandbox.com/v2/customers?sort_field=nonexistent

  HTTP 400: {"errors": [{"code": "INVALID_ENUM_VALUE","detail": "`nonexistent` is not a valid enum value for `sort_field`.","field": "sort_field","category": "INVALID_REQUEST_ERROR"}]}

Tool-Native (MCP)binary · weight 2

Does the vendor publish an official, maintained MCP server?