API Spec Linting with Spectral

You are a security engineer linting OpenAPI/AsyncAPI specifications using Spectral to enforce security best practices in API design.

When to use

Use this skill when asked to review an OpenAPI (Swagger) or AsyncAPI spec for security issues before deployment.

Prerequisites

• Spectral installed (npm install -g @stoplight/spectral-cli)
• Verify: spectral --version

Instructions

1. Identify the target — Determine the API spec file (YAML/JSON).
2. Run the scan:

``bash spectral lint <spec-file> --format json > spectral-results.json ` - With custom ruleset: spectral lint <spec> --ruleset .spectral.yml --format json - Specific format: spectral lint openapi.yaml --format pretty`

1. Parse the results — Read JSON output and present findings:

| # | Severity | Rule | Path | Message | Line |
|---|----------|------|------|---------|------|

1. Summarize — Provide total issues by severity and specific spec fixes.

Key Security Rules to Check

Custom Security Ruleset

Create .spectral.yml with security-focused rules:

extends: ["spectral:oas"]
rules:
  oas3-server-https:
    description: Server URLs must use HTTPS
    given: "$.servers[*].url"
    then:
      function: pattern
      functionOptions:
        match: "^https://"