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    🛡️OpenAPI Contract Guard

    🛡️OpenAPI Contract Guard

    by JustHandled Labs

    Lint an OpenAPI spec and diff two versions to catch breaking API changes before they reach consumers. Within a spec it flags missing operationId, success responses with no schema, untyped parameters, operations with no security requirement, and unbounded arrays/strings. Across two versions it flags removed paths and operations, removed response codes, a parameter becoming required, narrowed parameter types, removed enum values, and removed response fields. Analyzes JSON specs (convert YAML to JSON first).

    Updated Jun 2026
    Security scanned
    Cursor

    $12

    · or 60 credits

    30-day refund guarantee

    Secure checkout via Stripe

    Included in download

    • Identify breaking changes between two versions of an OpenAPI spec
    • Audit Swagger files for missing documentation and style violations
    • terminal, file_read automation included
    • Ready for Cursor
    • Instant install

    Sample input

    Check schema/v1.json and schema/v2.json for breaking changes and lint errors.

    Sample output

    API Contract Audit

    [BREAKING] OAS-DIFF-001: Removed property user_id from User schema. [WARNING] OAS-LINT-024: Missing description for GET /orders.

    Remediation: Restore user_id or mark as deprecated if transitioning to uuid.

    About This Skill

    What it does

    OpenAPI Contract Guard is a specialized developer tool designed to catch breaking changes and linting violations in your API specifications before they reach production. It analyzes OpenAPI and Swagger files to identify risks that could impact downstream consumers, such as removed endpoints, modified property types, or missing documentation.

    Why use this skill

    Manual API reviews are error-prone and time-consuming. This skill automates the detection of "silent breakages" that simple linters often miss. It provides a structured heuristic analysis of the differences between two versions of a spec, ensuring your team maintains strict backward compatibility. By integrating this into your workflow, you prevent broken client integrations and reduce the overhead of manual contract testing.

    • Automated Breaking Change Detection: Instantly identifies removals or modifications of existing endpoints and fields.
    • Comprehensive Linting: Surfaces style and structural issues following best practices.
    • Remediation Guidance: Every finding includes technical evidence and specific steps to fix the issue.
    • Format Agnostic: While the core scanner processes JSON, the skill handles YAML-to-JSON conversion seamlessly.

    Supported tools

    Supports OpenAPI 3.x and Swagger 2.0 specifications in both JSON and YAML formats. It uses a custom Python-based heuristic engine for deep diff analysis.

    Use Cases

    • Identify breaking changes between two versions of an OpenAPI spec
    • Audit Swagger files for missing documentation and style violations
    • Prevent deployment of APIs that would break downstream client apps
    • Generate remediation guides for API schema inconsistencies

    Reviews

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    Security Scanned

    Passed automated security review

    Permissions

    Terminal / Shell
    Read Files

    File Scopes

    openapi-contract-guard/**
    **/openapi*.json
    **/openapi*.yaml
    **/openapi*.yml
    **/swagger*.json
    **/swagger*.yaml
    **/swagger*.yml
    **/*.openapi.json
    **/*.openapi.yaml

    Read-only. Parses JSON with the standard library (no PyYAML). Convert YAML specs to JSON before scanning; non-JSON input is flagged with OAS000 as a reminder. Reads no environment variables.

    Tags

    openapi
    api-design
    swagger
    backend
    contract-testing

    Works with any agent that can read spec files and run a local Python script (Claude Code, Cursor, Codex CLI, and other SKILL.md-compatible agents). Standard library only, no install step. The scanner analyzes JSON; if a spec is YAML or Swagger YAML, the agent converts it to JSON first as a workflow step. Read-only.

    Creator

    JustHandled Labs

    JustHandled Labs creates focused agent skills and workflow packs for Claude, Codex, Cursor, and AI-assisted builders. Each tool is designed around a real repeatable task: cleaner commits, better PRs, stronger handoffs, safer repo hygiene, clearer documentation, and less copy-paste chaos. The goal is not generic AI productivity. The goal is specific workflows that are easier to run, review, and repeat. Maintained by H.J. Westerfield, with a background in communications, editing, project coordination, customer support, and practical AI systems. JustHandled Labs builds tools for people who want useful automation without theatrical complexity.

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