# suffix.agency

> Free, agent-first HTTP API to compare registrar domain prices, check availability (including premiums), and obtain executable purchase plans for registrars using the end user's own account and payment method.

Canonical host: **https://suffix.agency**
Legacy host **prefix.domains** redirects here.

## What you should know

- We are not a registrar or reseller. Domains register into YOUR registrar account; YOU pay the registrar.
- Purchase plans assume a cold start: create account or log in, verify email, add payment, then buy. They do not assume you already have registrar API keys.
- Each purchase-plan response lists `prerequisites` up front (email, card, registrant contact, etc.) and `steps` that may branch with `when` (e.g. `account.exists == false` vs `true`).
- Read `validation` on every purchase-plan. `live_register_proven` is false unless a live register has been proven. Prefer `harness_mock_executed` / `documented_api_mock_tested` over `template_unverified`, and be ready to adapt browser selectors.
- Your agent needs: HTTP, browser, email, payment, and secrets storage (SMS only if the registrar requires it).
- Availability statuses are definitive only: `taken`, `available`, `unknown`, `invalid`.
- `available` always includes a stated register price from a registrar check. `taken` is confirmed via registry lookup.
- List prices are standard TLD retail snapshots (`price_class=standard_list`). Premiums require a live quote (`price_class=premium`) plus `accept_premium: true` and matching `accept_price_cents` before a purchase-plan is `ready`.
- Default price ranking uses register (year-1) price. Pass `optimize=tco_2y` or `optimize=renew` for other orderings.
- No MCP. Use OpenAPI: /openapi.json
- No API keys for suffix.agency; expect IP rate limits on availability/quote/suggest/purchase-plan.

## Endpoints

- GET /v1/registrars
- GET /v1/prices?tld=
- GET /v1/compare?domain=&optimize=register|tco_2y|renew
- POST /v1/availability
- POST /v1/quote
- POST /v1/purchase-plan
- POST /v1/suggest
- GET /v1/health
- GET /llms.txt
- GET /openapi.json