| name | agent-authoring |
| description | **WORKFLOW SKILL** — Creates, restructures, and audits GitHub Copilot `.agent.md` and `.prompt.md` files with correct frontmatter, handoffs, model policy, context budgets, and validation. WHEN: "create agent", "author custom agent", "edit agent definition", "agent architecture", "reduce agent tokens", "agent prompt audit". DO NOT USE FOR: routine edits covered by auto-loaded instructions. |
| license | MIT |
| metadata | {"author":"jonathan-vella","version":"1.0","category":"agent-development"} |
Agent Authoring
Create and restructure Copilot agents without loading extended authoring guidance
into every ordinary agent turn. The thin enforcement layer remains in
agent-authoring.instructions.md.
When To Use This Skill
- Create a new
.agent.md or .prompt.md.
- Restructure an oversized or duplicated agent definition.
- Design handoffs or subagent boundaries.
- Select or upgrade an agent model.
- Audit fixed context cost, tool scope, or prompting structure.
- Investigate an agent validation failure requiring more than a local fix.
Do not load this skill for a routine edit where the thin instruction already
states the applicable rule.
Prerequisites
- Read the target file and its nearest analogous agent once.
- Check
.github/skills/workflow-engine/templates/workflow-graph.json before
changing workflow topology.
- Check
.github/model-catalog.json before changing model labels.
- Preserve user changes and existing runtime contracts.
Workflow
1. Classify The Change
Choose the smallest applicable path:
Load only the references needed for the selected path.
2. Establish Ownership
Keep each concern in one place:
- Agent body: role, goal, workflow-specific constraints, output, stop rules.
- Instruction: enforceable rules that apply automatically by file type.
- Skill: on-demand domain workflow and decision guidance.
- Reference: detailed examples, rationale, matrices, and troubleshooting.
- Registry or graph: machine-readable inventory and topology.
Do not copy canonical tables or templates into an agent body.
3. Budget Context
- Target 350 body lines or fewer; never exceed the enforced 600-line ceiling.
- Keep tool lists minimal and handoffs intentional.
- Move templates longer than 50 lines to references or templates.
- Prefer one structured example under 12 lines.
- Remove prose already supplied by an auto-loaded instruction.
- Estimate fixed cost using body bytes, matched instruction bytes, tool schemas,
and mandatory skill reads.
Use the context-management skill for runtime compression or debug-log audits.
4. Implement Incrementally
- Update frontmatter and the smallest body section first.
- Run the focused agent validator.
- Move optional detail into references only after behavior remains valid.
- Update model registry or workflow graph mirrors when their canonical source
changes.
- Update documentation when an agent or skill is added, renamed, or removed.
5. Validate
Run:
npm run validate:agents
npm run lint:vendor-prompting
npm run validate:model-consistency
npm run validate:skills
npm run lint:md
For model changes also run npm run validate:model-catalog and
npm run validate:deprecated-models.
Output Expectations
Return:
- Files changed and ownership rationale
- Fixed-context reduction when slimming an agent
- Preserved runtime contracts and anchors
- Validation commands and results
- Any documentation or generated inventory updated
Troubleshooting
| Symptom | Action |
|---|
| Agent is not discovered | Validate frontmatter, filename, description form, and model syntax |
| Handoff fails validation | Verify target name, allowed fields, and input/output enrichment |
| Skill is reported orphaned | Reference .github/skills/agent-authoring/SKILL.md canonically |
| Model consistency fails | Treat agent frontmatter as canonical, then update registry mirrors |
| Context remains large | Remove duplicated instruction prose and move phase-specific detail to references |
Reference Index
