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API Conditional Requests Validation

Implement conditional request validators for safe concurrency: strong/weak ETags, If-Match/If-Unmodified-Since, 412 and 428. Use when preventing lost updates on PUT/PATCH/DELETE.

deangrant 56e6a1c 4 files · 2.0 KB Updated
Integrations & APIs

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Conditional Requests and Validation

Use this skill for optimistic concurrency on mutations.

1. Preconditions

Header Typical use
If-Match Mutate only if ETag matches (strong)
If-None-Match GET revalidation / create-if-absent patterns
If-Unmodified-Since Time-based precondition

Mismatch → 412 Precondition Failed. Missing required precondition may be 428 Precondition Required. Business conflict → 409.

2. Strong vs weak ETags

Use strong ETags when byte-identity matters for writes. Weak ETags (W/) are for semantic equivalence / caching, not safe lost-update prevention.

3. Quick checklist

  • Strong ETag on contested resources.
  • Require If-Match on PUT/PATCH (and DELETE if needed).
  • 412 / 428 / 409 distinguished correctly.
  • Precedence rules documented.

See reference.md and examples.md.

deangrant/agents/tree/main/.agents/skills/api-conditional-requests-validation commit 56e6a1cb4e

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npx skillmds@latest add deangrant/api-conditional-requests-validation