# Fonoa vs Quaderno

> Quaderno scores 59.5 (C) on agent readiness against Fonoa's 51.7 (D), and leads in 4 of 7 scored categories. Fonoa leads on agent ergonomics, security & auth and maintenance & community. Both do tax calculate. Category scores, facts, verdicts and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/fonoa-vs-quaderno
- Markdown: https://www.anchorterminal.com/compare/fonoa-vs-quaderno.md (~2,150 tokens)
- Slim: https://www.anchorterminal.com/compare/fonoa-vs-quaderno.min.md (~730 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/fonoa-vs-quaderno.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

Quaderno scores 59.5 (C) on agent readiness against Fonoa's 51.7 (D), and leads in 4 of 7 scored categories. Fonoa leads on agent ergonomics, security & auth and maintenance & community. Both do tax calculate.

- Fonoa: grade D, 51.7/100, rank #575 of 722. Markdown https://www.anchorterminal.com/tools/fonoa.md · JSON https://www.anchorterminal.com/api/v1/tools/fonoa.json
- Quaderno: grade C, 59.5/100, rank #427 of 722. Markdown https://www.anchorterminal.com/tools/quaderno.md · JSON https://www.anchorterminal.com/api/v1/tools/quaderno.json

## Which one, for what

### Fonoa (D)

Good for: An agent working for a company that already has a Fonoa contract and needs tax ID validation, VAT or GST calculation, or e-invoice reporting across many countries through one API.

Ahead on:
- Agent ergonomics, 64 against 56
- Security & auth, 47 against 39
- Maintenance & community, 49 against 28

Watch for: No self-serve signup. Sandbox, demo and production keys are issued by Fonoa after contact by email or the sales form

### Quaderno (C)

Good for: An agent working for a SaaS, digital-goods or e-commerce seller that needs a tax rate at checkout, a record of each sale with location evidence, and compliant invoices, including Spanish Verifactu and TicketBAI.

Ahead on:
- Reliability, 91 against 66
- Schema & documentation, 77 against 68
- Payments & pricing, 30 against 3
- Transparency & trust, 76 against 48

Watch for: One API key reads and writes everything its user can reach. Scopes exist only on Connect OAuth tokens (read_only, read_write)


## Score by category

| Category | Weight | Fonoa | Quaderno | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 66 | 91 | Quaderno +25 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 68 | 77 | Quaderno +9 |
| Agent ergonomics | 13% (16.2 this run) | 64 | 56 | Fonoa +8 |
| Security & auth | 14% (17.5 this run) | 47 | 39 | Fonoa +8 |
| Payments & pricing | 10% (12.5 this run) | 3 | 30 | Quaderno +27 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 49 | 28 | Fonoa +21 |
| Transparency & trust | 7% (8.8 this run) | 48 | 76 | Quaderno +28 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **51.7 · D** | **59.5 · C** | |

## Facts side by side

| Fact | Fonoa | Quaderno |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Fonoa Technologies Limited | Recrea Systems, SL |
| Hosted endpoint | `https://api.fonoa.com` | `https://quadernoapp.com/api` |
| Transports | HTTP | HTTP |
| Auth | API key | OAuth or key |
| Pricing | Paid | Paid |
| x402 | no | no |
| Licence | Proprietary service. The API contract is not published. The public Terms of Service took effect on 14 May 2020 and name older seller sites | Proprietary service under Quaderno's terms of service. The Ruby library on GitHub is MIT |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-02 | 2026-07-04 |
| Terms last updated | no document linked | 2026-09-15 |
| Privacy policy last updated | no date given | 2024-05-16 |
| Customer content may train models |  | not found in the text |
| Terms restrict automated access |  | yes |
| Terms restrict benchmarking |  | yes |
| Terms or service can change without notice |  | yes |
| Arbitration or class-action waiver |  | not found in the text |
| Popularity | none | 15 stars |

## Verdicts

**Fonoa.** The API reference is served as Markdown with an OpenAPI definition on each endpoint page, and e-invoicing submissions are idempotent by `transaction_id`. API keys are issued by Fonoa staff after contact, no price, rate limit or changelog is published, and the only public terms date from May 2020 and cover older seller sites.

**Quaderno.** A public OpenAPI 3.1 spec covers 92 operations, with a free sandbox and a status page showing no incident since July 2025. The API key has full account access, there are no idempotency keys, and the newest public API version is dated October 2024.

## Before you call either

### Fonoa

1. Send the key in the `Ocp-Apim-Subscription-Key` header. Use the sandbox key at https://sandbox.fonoa.com and the production key at https://api.fonoa.com
2. Treat validations and e-invoicing submissions as asynchronous. POST, then poll the GET endpoint or wait for the webhook, and avoid tight polling
3. Reuse the same `transaction_id` on a retry of `/v1/transactions`. A transaction already processed is not processed again
4. Commit a calculation with POST `/tax/v2/calculations/<uuid>/commit` only when the sale is final. The commit adds it to revenue tracking
5. Ask the Fonoa contact to configure webhooks. There is no API for it, and always fetch `resource_url` as given in the webhook

### Quaderno

1. Call GET https://quadernoapp.com/api/authorization first. Its `href` gives the account subdomain that every other call needs
2. Before retrying a failed POST /transactions, list invoices by `processor_id` to check whether the sale was recorded. There is no idempotency key
3. Treat GET /invoices/{id}/deliver as a write. It emails the invoice to the customer
4. Correct a final invoice with a credit note. DELETE on invoices returns 410 and PUT accepts only notes, tags, metadata and address fields
5. Read X-RateLimit-Remaining and X-RateLimit-Reset, and page with `created_before` and `limit` up to 100

## Questions

### Which is better for AI agents, Fonoa or Quaderno?

Quaderno scores 59.5 (C) on agent readiness against Fonoa's 51.7 (D), and leads in 4 of 7 scored categories. Fonoa leads on agent ergonomics, security & auth and maintenance & community.

### Do Fonoa and Quaderno need an API key?

Fonoa needs an API key. Quaderno takes an API key or an OAuth sign-in.

### Can an agent call Fonoa and Quaderno without installing anything?

Yes. Fonoa has a hosted endpoint at https://api.fonoa.com and Quaderno at https://quadernoapp.com/api.


## For agents

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

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