Head to head · Tax calculate · October 2026 research run
Fonoa vs Zamp
Fonoa scores 51.7 (D) on agent readiness against Zamp's 49.5 (D), and leads in 3 of 7 scored categories. Zamp leads on reliability and payments & pricing. Both do tax calculate.
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
- Schema & documentation, 68 against 44
- Security & auth, 47 against 40
- Maintenance & community, 49 against 42
Watch for
No self-serve signup. Sandbox, demo and production keys are issued by Fonoa after contact by email or the sales form
Zamp D
Good for An agent working for a US or Canadian seller that wants Zamp's team to register, file and remit, and needs calculation and transaction sync through a small API.
Ahead on
- Reliability, 72 against 66
- Payments & pricing, 20 against 3
Also in its favour
- Free to start without a card
Watch for
No OpenAPI file for the API. The one file on the docs host is the documentation platform's plant store sample
Score by category
| Category | Weight this run | Fonoa | Zamp | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 66 | 72 | Zamp +6 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 68 | 44 | Fonoa +24 |
| Agent ergonomics | 13%16.2 | 64 | 64 | even |
| Security & auth | 14%17.5 | 47 | 40 | Fonoa +7 |
| Payments & pricing | 10%12.5 | 3 | 20 | Zamp +17 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 49 | 42 | Fonoa +7 |
| Transparency & trust | 7%8.8 | 48 | 50 | Zamp +2 |
| Negative events | ≤15 | 0 | 0 | |
| Total | 51.7 · D | 49.5 · D |
Facts side by side
| Fact | Fonoa | Zamp |
|---|---|---|
| Kind | HTTP API | HTTP API |
| Vendor | Fonoa Technologies Limited | Zamp Inc. |
| Hosted endpoint | https://api.fonoa.com | https://api.zamp.com |
| Transports | HTTP | HTTP |
| Auth | API key | API 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 Zamp's Standard Terms and Conditions, which form part of a signed Order Form. The sandbox has its own Developer trial terms |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-10-02 | 2026-08-31 |
| Terms last updated | no document linked | no date given |
| Privacy policy last updated | no date given | 2025-02-11 |
| 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 | not found in the text | |
| Arbitration or class-action waiver | not found in the text |
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.
Zamp
A free 30-day sandbox key needs no card or sales call, and the docs are served as Markdown with llms.txt and a published limit of 1,000 requests a minute. There is no OpenAPI file, SDK, API changelog or published price, production keys come with a sales-led account, and the site footer says SOC 2 compliance is in progress.
Before you call either
Fonoa
- Send the key in the
Ocp-Apim-Subscription-Keyheader. Use the sandbox key at https://sandbox.fonoa.com and the production key at https://api.fonoa.com - Treat validations and e-invoicing submissions as asynchronous. POST, then poll the GET endpoint or wait for the webhook, and avoid tight polling
- Reuse the same
transaction_idon a retry of/v1/transactions. A transaction already processed is not processed again - Commit a calculation with POST
/tax/v2/calculations/<uuid>/commitonly when the sale is final. The commit adds it to revenue tracking - Ask the Fonoa contact to configure webhooks. There is no API for it, and always fetch
resource_urlas given in the webhook
Zamp
- Call
POST /calculationsfor a quote andPOST /transactionsonly when the sale is final. Put the returnedtaxDueintaxCollectedwhen posting - Keep transaction and line item ids to 25 characters. A repeated
POST /transactionswith an existing id returns 409CONFLICT, so a retry doesn't create a second record - For a refund, post a new transaction with
parentIdset to the sale's id and a negativequantity. Never send a negativeamounton a line item - Send
shipToAddress.stateandcountryset to CA for Canadian orders.POST /addressesvalidates US addresses only - Page lists with
limit(1 to 100, default 10) andcursoruntilnextCursoris null.GET /transactionsreturns only transactions written with the same key - Don't store sensitive or personal data in the sandbox. Trial data is deleted after 30 days and the trial terms forbid live customer data
Questions
Which is better for AI agents, Fonoa or Zamp?
Fonoa scores 51.7 (D) on agent readiness against Zamp's 49.5 (D), and leads in 3 of 7 scored categories. Zamp leads on reliability and payments & pricing.
Do Fonoa and Zamp need an API key?
Both need an API key.
Can an agent call Fonoa and Zamp without installing anything?
Yes. Fonoa has a hosted endpoint at https://api.fonoa.com and Zamp at https://api.zamp.com.
Other comparisons with Fonoa or Zamp
Machine-readable
- This page as Markdown
/compare/fonoa-vs-zamp.md· slim.min.md· JSON.json(or sendAccept: text/markdown) - Each listing in full
/api/v1/tools/fonoa.json·/api/v1/tools/zamp.json - From a terminal
anchor compare fonoa zamp(the CLI) - Over MCP
compare_tools {"a": "fonoa", "b": "zamp"}at/mcp, no key