SKILL.md
API Compatibility Check
Detect breaking changes in API definitions. Read-only analysis, safe to re-run.
1. Prerequisites
Check for specialized tools via command -v: buf (protobuf), oasdiff (OpenAPI). Report availability. If missing, fall back to manual git-diff analysis and note which tool would improve accuracy.
2. Scope
If $ARGUMENTS names specific files, analyze only those. Otherwise, find API files changed since base branch using git diff --name-only $(git merge-base HEAD main). Detect by pattern:
| Pattern | Type |
|---|---|
*.proto |
Protobuf |
openapi.yaml, swagger.json, .openapi., .swagger. |
OpenAPI |
.graphql, .gql |
GraphQL |
*.go with exported types changed |
Go exported API |
Stop with a clear message if no API files are found in scope.
3. Baseline
Compute and print the merge-base: git merge-base HEAD main. For each file in scope, diff working tree against that baseline using git diff <merge-base> -- <file>.
4. Analysis by Type
Protobuf
If buf is available, run buf breaking --against .git#ref=<merge-base>. Otherwise, manually inspect diffs for:
- BREAKING: field number reuse, field removal, type change, adding required fields
- SAFE: new optional field, new enum value with no renumbering
OpenAPI
If oasdiff is available, run oasdiff breaking <base-file> <current-file>. Otherwise, manually inspect diffs for:
- BREAKING: removed endpoint, changed HTTP method, removed parameter, new required parameter, response schema narrowing
- SAFE: new optional parameter, new endpoint, added response fields
GraphQL
Manually inspect diffs for:
- BREAKING: removed type/field, changed return type, new required argument, removed enum value
- SAFE: new optional field/argument, new type, new enum value
Go Exported API
Manually inspect diffs for:
- BREAKING: removed exported symbol, changed function signature, changed interface method set, changed struct field types
- SAFE: new exported symbol, new method on concrete type
5. Output
Print a summary line first: total changes found, how many breaking. Then print a compatibility report table:
| Change | File:Line | Type | Severity |Severity values: BREAKING, WARN, SAFE. Use WARN when a change is technically non-breaking but likely to cause client issues (e.g., deprecating a widely-used field, adding an enum value to a closed enum).
6. Idempotency
Read-only. No files created, modified, or deleted. Safe to re-run at any time.
$ARGUMENTS