Direct positive evidence
A registry record or exact namespace match returned a decisive observation.
Domain availability API · authenticated v1
Domain evidence an agent can reason about.
Check one shortlist or a bounded batch without reducing registry behavior to an unreliable boolean. Each result preserves source, time, evidence state, confidence, and a manual registrar action.
curl -sS "https://namingsignal.com/api/v1/check" \
-H "Authorization: Bearer $NAMING_SIGNAL_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: shortlist-001" \
-d '{"names":["offhook","nicless"],"tlds":["com","app"]}'Calibrated absence
Registry not-found is trusted only after the same provider recognizes a known-registered canary.
Failure stays unresolved
Timeout, HTTP 429, failed calibration, unsupported provider, malformed response, or conflict.
Checkout still matters
The user verifies current price, premium status, fees, and registrability at a registrar.
Authentication
User-owned keys, never your Clerk secret
A person signs in with Clerk and creates a separately revocable key. REST, CLI, and MCP clients send that user key in the Authorization Bearer header. The server validates it with Clerk and charges the same account ledger used by signed-in browser sessions.
Free allowance
10,000 monthly Naming Credits
A name × TLD domain combination costs one credit. Generation, ranking, research, and public imports use weighted credits that reflect their relative provider cost. The allowance resets at the start of each UTC calendar month.
Abuse controls
Bounded batches and layered limits
The API validates body size, batch size, idempotency, account credits, and request policy before expensive work. Vercel firewall rules provide an additional IP burst layer without replacing account-level quotas.
Technical note
A 404 is not automatically availability.
Read the failure case and known-registered canary method behind NamingSignal's domain evidence policy.