Create Custom Agent

This skill guides you through creating a custom GitHub Copilot agent — an @-invokable chat participant that extends Copilot with domain-specific expertise. Custom agents are distinct from Agent Skills: skills provide reusable instructions loaded on demand, while agents own the full conversational interaction and can orchestrate tools, call APIs, and maintain their own prompt strategies.

When Not to Use

• Adding reusable, invokable workflows — use Agent Skills (.agents/skills/) instead
• Adding background coding guidelines — use file-based instructions (.github/instructions/) instead
• Adding project-wide context for Copilot — use .github/copilot-instructions.md instead
• Creating reusable prompts — use .prompt.md instead

Workflow

For an existing proposal, audit the full definition rather than just its tools: the description must identify natural requests that should discover it, the body must add domain knowledge beyond root instructions, and the paired eval must isolate its contribution. Compare every tool and behavior to the user's intended authority. A command-free reviewer must not gain command execution or publication through a wildcard tool, handoff, or otherwise read-only workflow.

Step 1: Choose the agent type