Vertex O Series vs Zamp

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.

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.

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

Zamp

1. Call POST /calculations for a quote and POST /transactions only when the sale is final. Put the returned taxDue in taxCollected when posting
2. Keep transaction and line item ids to 25 characters. A repeated POST /transactions with an existing id returns 409 CONFLICT, so a retry doesn't create a second record
3. For a refund, post a new transaction with parentId set to the sale's id and a negative quantity. Never send a negative amount on a line item
4. Send shipToAddress.state and country set to CA for Canadian orders. POST /addresses validates US addresses only
5. Page lists with limit (1 to 100, default 10) and cursor until nextCursor is null. GET /transactions returns only transactions written with the same key
6. 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