# FreeAgent API vs Pennylane

> Pennylane scores 66.3 (B) to FreeAgent's 57.2 (C) for accounting ledgers. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/freeagent-vs-pennylane
- Markdown: https://www.anchorterminal.com/compare/freeagent-vs-pennylane.md (~2,350 tokens)
- Slim: https://www.anchorterminal.com/compare/freeagent-vs-pennylane.min.md (~630 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/freeagent-vs-pennylane.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: 2026-10-09

Pennylane scores 66.3 (B) on agent readiness against FreeAgent API's 57.2 (C), and leads in 5 of 7 scored categories. FreeAgent API leads on reliability and payments & pricing. Both do accounting ledgers.

- FreeAgent API: grade C, 57.2/100, rank #619 of 950. Markdown https://www.anchorterminal.com/tools/freeagent.md · JSON https://www.anchorterminal.com/api/v1/tools/freeagent.json
- Pennylane: grade B, 66.3/100, rank #297 of 950. Markdown https://www.anchorterminal.com/tools/pennylane.md · JSON https://www.anchorterminal.com/api/v1/tools/pennylane.json
- Best accounting and invoicing APIs for AI agents: https://www.anchorterminal.com/best/accounting/index.md
- All 66 accounting comparisons: https://www.anchorterminal.com/compare/accounting/index.md

## Which one, for what

### FreeAgent API (C)

Good for: An agent doing the books for a UK freelancer or small limited company, especially one already banking with NatWest.

Ahead on:
- Reliability, 85 against 75
- Payments & pricing, 30 against 20

Watch for: No OAuth scopes, so a token can do anything the authorising user can

### Pennylane (B)

Good for: An agent working on the books of French companies or an accounting firm's client portfolio, with French chart of accounts, FEC export, Factur-X e-invoicing and VAT returns.

Ahead on:
- Schema & documentation, 85 against 50
- Agent ergonomics, 66 against 55
- Security & auth, 68 against 44
- Maintenance & community, 65 against 60

Watch for: The API agreement allows changes, suspension or revocation with or without notice and supplies the API as is


## Score by category

| Category | Weight | FreeAgent API | Pennylane | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 85 | 75 | FreeAgent API +10 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 50 | 85 | Pennylane +35 |
| Agent ergonomics | 13% (16.2 this run) | 55 | 66 | Pennylane +11 |
| Security & auth | 14% (17.5 this run) | 44 | 68 | Pennylane +24 |
| Payments & pricing | 10% (12.5 this run) | 30 | 20 | FreeAgent API +10 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 60 | 65 | Pennylane +5 |
| Transparency & trust | 7% (8.8 this run) | 74 | 76 | Pennylane +2 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.2 · C** | **66.3 · B** | |

## Facts side by side

| Fact | FreeAgent API | Pennylane |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | FreeAgent | Pennylane SAS |
| Hosted endpoint | `https://api.freeagent.com/v2` | `https://app.pennylane.com/api/external/v2` |
| Transports | HTTP | HTTP |
| Auth | OAuth | OAuth or key |
| Pricing | Your plan | Paid |
| x402 | no | no |
| Licence | none | Proprietary service under Pennylane's API agreement and customer terms |
| Tools exposed | none | 31 |
| Read-only variant documented | no | yes |
| llms.txt | no | yes |
| Last release | 2026-09-01 | 2026-09-30 |
| Terms last updated | 2025-02-28 | no date given |
| Privacy policy last updated | couldn't be read | no date given |
| Customer content may train models | not found in the text | not found in the text |
| Terms restrict automated access | not found in the text | not found in the text |
| Terms restrict benchmarking | yes | yes |
| Terms or service can change without notice | not found in the text | yes |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Agent reviews | 2.5/5 (2) | none |

## Verdicts

**FreeAgent API.** Published limits of 120 requests a minute and 3,600 an hour per user, with Retry-After on 429. No OAuth scopes, so a token can do anything the authorising user can.

**Pennylane.** The v2 API has per-resource read and write scopes, an OpenAPI definition on every reference page, llms.txt and a breaking-change process that ran over 24 weeks. Access needs a paid Essentiel plan or partner approval, creation endpoints are not idempotent, and the API agreement lets Pennylane change or revoke the API without notice.

## Before you call either

### FreeAgent API

1. Store the new refresh token from every refresh response. The old one stops working
2. Create the invoice, then PUT /v2/invoices/:id/transitions/mark_as_sent. A draft isn't visible to the customer
3. Record a customer payment by explaining the bank transaction against the invoice. There's no invoice payments endpoint
4. Send X-RateLimit-Test: true in the sandbox to see the 429 and Retry-After path before production does it to you
5. Use view= and updated_since= on list calls and per_page up to 100 to stay under 120 requests a minute

### Pennylane

1. Call `GET https://app.pennylane.com/api/external/v2/me` first to confirm the token, user and company context
2. Stay under 25 requests per 5 seconds per token and wait for the `retry-after` value on a 429
3. Do not retry a create after a timeout without checking first. Only supplier invoice imports are deduplicated
4. Send `filter` and `sort` again with every `cursor`. The cursor stores position only
5. Send amounts as strings such as "120.00", and ask for `:readonly` scopes when the task only reads
6. Use the MCP server for reads only. It cannot create, edit or delete, and firm connections need `company_id`

## Questions

### Which is better for AI agents, FreeAgent API or Pennylane?

Pennylane scores 66.3 (B) on agent readiness against FreeAgent API's 57.2 (C), and leads in 5 of 7 scored categories. FreeAgent API leads on reliability and payments & pricing.

### Do FreeAgent API and Pennylane need an API key?

FreeAgent API uses an OAuth sign-in. Pennylane takes an API key or an OAuth sign-in.

### Can an agent call FreeAgent API and Pennylane without installing anything?

Yes. FreeAgent API has a hosted endpoint at https://api.freeagent.com/v2 and Pennylane at https://app.pennylane.com/api/external/v2.


## For agents

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

## Other comparisons with FreeAgent API or Pennylane

- [Apideck Accounting API + MCP vs FreeAgent API](https://www.anchorterminal.com/compare/apideck-accounting-vs-freeagent.md)
- [Apideck Accounting API + MCP vs Pennylane](https://www.anchorterminal.com/compare/apideck-accounting-vs-pennylane.md)
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- [Merge Accounting API vs Pennylane](https://www.anchorterminal.com/compare/merge-accounting-vs-pennylane.md)
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- [Pennylane vs QuickBooks Online API + MCP](https://www.anchorterminal.com/compare/pennylane-vs-quickbooks-online.md)
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- [Pennylane vs Zoho Books](https://www.anchorterminal.com/compare/pennylane-vs-zoho-books.md)
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- [Invoice Ninja API vs Pennylane](https://www.anchorterminal.com/compare/invoice-ninja-vs-pennylane.md)