COP-008: Custom Agent Unknown Frontmatter Field

Summary

• Rule ID: COP-008
• Severity: MEDIUM
• Category: GitHub Copilot
• Normative Level: SHOULD
• Auto-Fix: Yes (safe)
• Verified On: 2026-02-13

Applicability

• Tool: github-copilot
• Version Range: unspecified
• Spec Revision: unspecified

Evidence Sources

• https://docs.github.com/en/copilot/reference/custom-agents-configuration

Test Coverage Metadata

• Unit tests: true
• Fixture tests: true
• E2E tests: false

Examples

The following examples demonstrate what triggers this rule and how to fix it.

Invalid

---
description: Review pull requests
mystery-field: true
---
Review pull requests.

Valid

---
description: Review pull requests
target: vscode
---
Review pull requests.