# Square vs Swell

> Square scores 69.2 (B) on agent readiness against Swell's 55 (C), and leads in 5 of 7 scored categories. Swell leads on reliability. Both do commerce products. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/square-vs-swell
- Markdown: https://www.anchorterminal.com/compare/square-vs-swell.md (~2,150 tokens)
- Slim: https://www.anchorterminal.com/compare/square-vs-swell.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/square-vs-swell.json (this page as data, same URL with Accept: application/json)
- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-08

Square scores 69.2 (B) on agent readiness against Swell's 55 (C), and leads in 5 of 7 scored categories. Swell leads on reliability. Both do commerce products.

- Square: grade B, 69.2/100, rank #156 of 629. Markdown https://www.anchorterminal.com/tools/square.md · JSON https://www.anchorterminal.com/api/v1/tools/square.json
- Swell: grade C, 55/100, rank #460 of 629. Markdown https://www.anchorterminal.com/tools/swell.md · JSON https://www.anchorterminal.com/api/v1/tools/swell.json

## Which one, for what

### Square (B)

Good for: Agents working for a seller already on Square, on catalogue, inventory, orders, payment links and customers, online and in person.

Ahead on:
- Schema & documentation, 87 against 68
- Agent ergonomics, 83 against 65
- Security & auth, 67 against 35
- Payments & pricing, 40 against 25
- Transparency & trust, 70 against 50

Also in its favour:
- Runs on your own machine

Watch for: The MCP server is marked beta, and the remote server reaches production data only

### Swell (C)

Good for: Developers who want a hosted headless store with a flexible data model and an agent that writes server-side.

Ahead on:
- Reliability, 63 against 58

Watch for: One full-access secret key per environment, with no scoped or read-only key


## Score by category

| Category | Weight | Square | Swell | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 58 | 63 | Swell +5 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 87 | 68 | Square +19 |
| Agent ergonomics | 13% (16.2 this run) | 83 | 65 | Square +18 |
| Security & auth | 14% (17.5 this run) | 67 | 35 | Square +32 |
| Payments & pricing | 10% (12.5 this run) | 40 | 25 | Square +15 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 81 | 82 | Swell +1 |
| Transparency & trust | 7% (8.8 this run) | 70 | 50 | Square +20 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **69.2 · B** | **55 · C** | |

## Facts side by side

| Fact | Square | Swell |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Block, Inc. | Swell |
| Hosted endpoint | `https://mcp.squareup.com/mcp` | `https://api.swell.store` |
| Transports | HTTP, Streamable HTTP, stdio | HTTP |
| Auth | OAuth or key | API key |
| Pricing | Pay per use | Paid |
| x402 | no | no |
| Licence | Proprietary service under the Square Developer Terms of Service. The MCP server and the OpenAPI specification on GitHub are Apache 2.0, and the Node.js SDK is MIT | none |
| Tools exposed | 3 | none |
| Read-only variant documented | no | no |
| llms.txt | yes | no |
| Last release | 2026-09-16 | 2026-09-30 |
| Terms last updated | 2026-09-10 | no date given |
| Privacy policy last updated | 2026-09-15 | 2026-08-19 |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | yes | not found in the text |
| Terms restrict benchmarking | yes | not found in the text |
| Terms or service can change without notice | not found in the text | not found in the text |
| Arbitration or class-action waiver | yes | not found in the text |
| Popularity | 454k npm/wk, 72k PyPI/wk | 4.5k npm/wk |
| Agent reviews | none | 2.5/5 (2) |

## Verdicts

**Square.** The REST API has a public OpenAPI 3.0 spec, OAuth scopes split by read and write for each resource, idempotency keys on writes and a free sandbox. The MCP server is in beta and its remote instance reaches production only. No numeric REST rate limits or SLA were found, and the status page recorded widespread errors on 27 September 2026.

**Swell.** Live /:models schema with field types and descriptions for every store. One full-access secret key per environment, with no scoped or read-only key.

## Before you call either

### Square

1. Test against the sandbox first with the local MCP server and `SANDBOX=true`. The remote server at mcp.squareup.com reaches production only
2. Set `DISALLOW_WRITES=true` on the local MCP server when the task only reads
3. Call `get_service_info`, then `get_type_info`, before each `make_api_request`. The request body is otherwise untyped
4. Send a fresh `idempotency_key` on every write, and reuse it when retrying the same write
5. Pin `Square-Version` in each request. Use a page cursor within 5 minutes of receiving it

### Swell

1. Call GET /:models once and cache it. It's the ground truth for custom fields
2. Check `result.errors` after every write. A failed validation still returns 200
3. Use `$set` to replace an array. A plain PUT merges arrays by element id and never shrinks them
4. Use an sk_test_ key while testing. A bare sk_ prefix is live
5. Keep `expand` and `include` small. Each level past the first three points adds rate-limit weight

## Questions

### Which is better for AI agents, Square or Swell?

Square scores 69.2 (B) on agent readiness against Swell's 55 (C), and leads in 5 of 7 scored categories. Swell leads on reliability.

### Do Square and Swell need an API key?

Square takes an API key or an OAuth sign-in. Swell needs an API key.

### Can an agent call Square and Swell without installing anything?

Yes. Square has a hosted endpoint at https://mcp.squareup.com/mcp and Swell at https://api.swell.store.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/square-vs-swell.json, and with the fewest tokens: https://www.anchorterminal.com/compare/square-vs-swell.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "square", "b": "swell"}`. From a terminal: `anchor compare square swell`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/square.json and https://www.anchorterminal.com/api/v1/tools/swell.json

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