# Compatibility Check

> Validate API compatibility across versions or consumers.

- Skill: `velcrafting/compatibility-check` (Agent Skill)
- Install (CLI): `npx skillmds@latest add velcrafting/compatibility-check`
- Raw SKILL.md: https://api.skillmd.com/api/skills/velcrafting/compatibility-check/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: velcrafting (https://skillmd.com/u/velcrafting)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/velcrafting/compatibility-check

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# Skill: api/compatibility-check

## Purpose
Determine whether an API change is:
- backward-compatible
- conditionally compatible
- breaking

And make that status explicit before shipping.

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## Inputs
- Old contract
- New contract
- Known consumers (if available)

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## Outputs
- Compatibility assessment:
  - compatible / breaking / unsafe
- Explicit list of breaking changes (if any)
- Recommendation:
  - proceed
  - version
  - block

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## Non-goals
- Modifying contracts
- Updating clients
- Implementing migrations

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## Workflow
1) Compare old vs new contract shapes.
2) Identify removed or behaviorally changed fields.
3) Assess consumer impact.
4) Emit a clear compatibility verdict.

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## Checks
- All removals and type changes enumerated
- Verdict is explicit and justified

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## Failure modes
- Missing baseline contract → block and request one.
- Ambiguous change → recommend `meta/spec-sculptor`.

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## Telemetry
Log:
- skill: `api/compatibility-check`
- verdict
- affected_consumers
- outcome