# Quaderno vs Vertex O Series

> Quaderno scores 59.5 (C) on agent readiness against Vertex O Series's 54.7 (C), and leads in 5 of 7 scored categories. Vertex O Series leads on 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/quaderno-vs-vertex-tax
- Markdown: https://www.anchorterminal.com/compare/quaderno-vs-vertex-tax.md (~2,000 tokens)
- Slim: https://www.anchorterminal.com/compare/quaderno-vs-vertex-tax.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
- JSON: https://www.anchorterminal.com/compare/quaderno-vs-vertex-tax.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 Vertex O Series's 54.7 (C), and leads in 5 of 7 scored categories. Vertex O Series leads on security & auth and maintenance & community. Both do tax calculate.

- Quaderno: grade C, 59.5/100, rank #377 of 629. Markdown https://www.anchorterminal.com/tools/quaderno.md · JSON https://www.anchorterminal.com/api/v1/tools/quaderno.json
- Vertex O Series: grade C, 54.7/100, rank #464 of 629. Markdown https://www.anchorterminal.com/tools/vertex-tax.md · JSON https://www.anchorterminal.com/api/v1/tools/vertex-tax.json

## Which one, for what

### 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 65
- Agent ergonomics, 56 against 51
- Payments & pricing, 30 against 0
- Transparency & trust, 76 against 68

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

### Vertex O Series (C)

Good for: An agent working inside a company that already has an O Series licence, for quotes, invoice tax, tax area lookups and tax configuration across sales tax, use tax and VAT.

Ahead on:
- Security & auth, 57 against 39
- Maintenance & community, 62 against 28

Watch for: No public price, free tier or self-serve signup. The security guide sends new users to the Vertex sales team for an account


## Score by category

| Category | Weight | Quaderno | Vertex O Series | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 91 | 65 | Quaderno +26 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 77 | 74 | Quaderno +3 |
| Agent ergonomics | 13% (16.2 this run) | 56 | 51 | Quaderno +5 |
| Security & auth | 14% (17.5 this run) | 39 | 57 | Vertex O Series +18 |
| Payments & pricing | 10% (12.5 this run) | 30 | 0 | Quaderno +30 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 28 | 62 | Vertex O Series +34 |
| Transparency & trust | 7% (8.8 this run) | 76 | 68 | Quaderno +8 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **59.5 · C** | **54.7 · C** | |

## Facts side by side

| Fact | Quaderno | Vertex O Series |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Recrea Systems, SL | Vertex, Inc. |
| Hosted endpoint | `https://quadernoapp.com/api` | `https://calcconnect.vertexsmb.com/vertex-ws/v2` |
| Transports | HTTP | HTTP |
| Auth | OAuth or key | OAuth |
| Pricing | Paid | Paid |
| x402 | no | no |
| Licence | Proprietary service under Quaderno's terms of service. The Ruby library on GitHub is MIT | Proprietary service under a customer agreement with Vertex, Inc. that isn't published |
| Read-only variant documented | no | no |
| llms.txt | yes | no |
| Last release | 2026-07-04 | 2026-09-25 |
| Terms last updated | 2026-09-15 | no date given |
| Privacy policy last updated | 2024-05-16 | no date given |
| 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 | yes | not found in the text |
| Arbitration or class-action waiver | not found in the text | not found in the text |
| Popularity | 15 stars | none |

## Verdicts

**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.

**Vertex O Series.** Public OpenAPI 3.0 specs cover calculation, transaction management, tax area lookup and tax configuration, and guides are served as Markdown. Access needs a sales contract. No price, free tier, sandbox signup, calculation rate limit, idempotency key or official SDK was found in the reviewed documentation.

## Before you call either

### 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

### Vertex O Series

1. Cache the access token for its 3,599-second life. The standard token endpoint allows 10 requests per 8 hours, and tokenguard.vertexcloud.com returns a cached token
2. Send no `Authorization: Bearer` header to /oauth/token, and put the client id and secret in the body or a Basic header. Credentials in the URL are rejected
3. Set `saleMessageType` to QUOTATION for an estimate. INVOICE is stored for reporting and remittance
4. Call GET /v2/transaction-exists/{transactionid} before retrying a failed INVOICE. No idempotency key is documented
5. Delete, reverse or roll back a Cloud transaction within 90 days of calculation. Later requests can cause calculation errors or duplicates

## Questions

### Which is better for AI agents, Quaderno or Vertex O Series?

Quaderno scores 59.5 (C) on agent readiness against Vertex O Series's 54.7 (C), and leads in 5 of 7 scored categories. Vertex O Series leads on security & auth and maintenance & community.

### Do Quaderno and Vertex O Series need an API key?

Quaderno takes an API key or an OAuth sign-in. Vertex O Series uses an OAuth sign-in.

### Can an agent call Quaderno and Vertex O Series without installing anything?

Yes. Quaderno has a hosted endpoint at https://quadernoapp.com/api and Vertex O Series at https://calcconnect.vertexsmb.com/vertex-ws/v2.


## For agents

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

## Other comparisons with Quaderno or Vertex O Series

- [Anrok vs Quaderno](https://www.anchorterminal.com/compare/anrok-vs-quaderno.md)
- [Anrok vs Vertex O Series](https://www.anchorterminal.com/compare/anrok-vs-vertex-tax.md)
- [Avalara AvaTax vs Quaderno](https://www.anchorterminal.com/compare/avalara-vs-quaderno.md)
- [Avalara AvaTax vs Vertex O Series](https://www.anchorterminal.com/compare/avalara-vs-vertex-tax.md)
- [Quaderno vs TaxJar](https://www.anchorterminal.com/compare/quaderno-vs-taxjar.md)
- [TaxJar vs Vertex O Series](https://www.anchorterminal.com/compare/taxjar-vs-vertex-tax.md)