# HTTP Entity-Tag Preconditions

Build-time release reference. Runtime readiness, deployment, payment settlement and external indexing are not evaluated here. Prices are proposed; this file cannot authorize execution or payment.

Evaluate supplied If-Match and If-None-Match against caller-asserted representation existence/current ETag, preserving strong/weak comparison and precondition order. Gives conditional 304/412 or proceed guidance only. Excludes date/range/freshness, duplicate-write exceptions, permission decisions and live requests.

Release: 0.29.0. Built: 2026-10-06T15:38:00Z.

## Choose for
- Evaluate conditional HTTP ETag cache validation and optimistic concurrency preconditions
- Distinguish weak If-None-Match from strong If-Match and wildcard existence

## Outside this profile
- Cache freshness, date validators, HTTP ranges, fetching resources or deciding replay authorization
- Guaranteed success status or inferring current representation from an ETag alone

Proposed nominal USD 0.003 per successful call; payer fees excluded. No verified runtime availability.

- [Exact release contract](/reference/services/http-etag-evaluate.json)
- [Input schema](/reference/schemas/http-etag-evaluate.input.json)
- [Output schema](/reference/schemas/http-etag-evaluate.output.json)
- [Fixed example](/reference/examples/http-etag-evaluate.json)
- [Complete HTML reference](/discover/tools/http-etag-evaluate)