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The Extended API is a set of low-latency edge utilities that complement the Main API. Use it for high-volume operations where round-trip latency matters: email address validation, DNS lookups for domain setup, SMS number validation, and AI subject-line scoring.

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Base URL

Both the Main API and Extended API now serve from the same hostname. The Extended API ships the wire-level conventions live today (Spotzee-Version, X-Request-Id, RFC 7807 error envelope). The Main API is rolling those conventions out in stages. See API conventions for the full set.

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Authentication

All requests require a bearer token. The same API keys used for the Main API are accepted here. See Authentication.

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Capabilities

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When to use Extended over Main

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Versioning

The Extended API is dated like the Main API. Pin a version with the Spotzee-Version request header (see API versioning). The current release is 2026-04-28. The OpenAPI specification is published at:

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Rate limits and quota

Two separate gates apply to Extended API traffic. Edge rate limit. Spotzee’s edge network enforces a per-source-IP cap of 1,000 requests per 10 seconds across apix.spotzee.com/api/*. Over-limit traffic receives 429 Too Many Requests with the canonical error envelope. The cap counts every request, authenticated or not. Credit-based quota. Validation, scoring, lookup, and generation endpoints deduct credits on success. The cost varies by route. Inspect remaining balance via the Quota endpoints before high-volume runs. Per-API-key sliding-window rate limits and a doubled budget for MCP traffic are rolling out alongside the Main API hardening rollout. The Extended API does not honour those today.

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Errors

See the Extended API errors reference.

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Next

Authentication

API keys and scopes.

Errors

Status codes and error bodies.