agent-skill-authoring

Agent & Skill Authoring

Overview

This skill defines the philosophy of the agent-vs-skill split and the conventions for writing skills. Agents own orchestration logic (when and why); skills own execution knowledge (how). This separation keeps agents readable as workflow definitions while keeping capabilities DRY across the team.

Scope boundary:

• This skill — skill creation, shared philosophy, anti-patterns, documentation sync policy
• agent-create skill — the procedural workflow for generating a new agent file (invoked by /agent-add)

If you are creating an agent file, use /agent-add (which invokes the agent-create skill). This skill no longer duplicates that procedure.

Constraints

• Skills must be agent-agnostic; no persona or behavioral logic in skill files
• Execution details belong in skills; orchestration logic belongs in agents
• Every new agent or skill must be registered (see references/templates.md)
• Do not embed a skill's knowledge inline in an agent — reference the skill file

Core Pattern

Agent (when + why)          Skill (how)
┌─────────────────┐        ┌─────────────────┐
│ ## Skills        │        │ # Skill Name    │
│ - Skill A ──────│───────>│                 │
│   "Invoke when  │        │ ## Concepts     │
│    designing    │        │ ## Patterns     │
│    bounded      │        │ ## Guidelines   │
│    contexts"    │        │ ## Structure    │
│                 │        │                 │
│ ## Behavioral   │        │ (reusable by    │
│   Guidelines    │        │  any agent)     │
│ (orchestration) │        │                 │
└─────────────────┘        └─────────────────┘

• Agents define the role: persona, behavior, collaboration style, and when/why to use each skill
• Skills define the capability: concepts, patterns, guidelines, and project structures
• An agent references a skill and annotates it with invocation context
• Multiple agents can share the same skill, each with different invocation context

Creating an Agent

Run /agent-add — it invokes the agent-create skill, which is the canonical procedure: name validation, type detection, scope-overlap check, body generation within token-efficiency budgets, /plugin-audit validation gate, and registry/CLAUDE.md updates.

Do not hand-author agent files when /agent-add is available — divergent templates produced manually have historically drifted from the schema enforced by /plugin-audit.

Creating a Skill

Resolve the target plugin directory ($PLUGIN) using the same convention as agent-create: --plugin <dir> argument; else single plugins/*/; else cwd ancestor with .claude-plugin/plugin.json; else ask.

Place skill files at $PLUGIN/skills/{skill-name}/SKILL.md. Use the skill template and authoring guidelines from references/templates.md. Then follow the registration checklist.

Meta-Patterns for Skill Writing

Before writing a new skill, read 2-3 existing skills in $PLUGIN/skills/ to absorb the project's voice and structure. Skills that follow existing patterns integrate better.

Explain the why, not just the what. LLMs follow rules more reliably when they understand the reasoning. "Do X because Y happens without it" beats "ALWAYS do X." Compare:

• Weak: "ALWAYS run tests before claiming done"
• Strong: "Run tests before claiming done — LLMs confidently claim 'done' without verification, and this is the single most common failure mode"

Include rationalization prevention. LLMs generate plausible excuses to skip hard steps. Add an "Excuses vs. Reality" table that pre-empts the common rationalizations for the skill's domain. This is the most effective compliance pattern in this project.

Use hard gates, not soft suggestions. "Should" is ignored; "must, with evidence" is followed. Gate pattern: require tool output (paste the result) as proof that a step was completed. Without evidence, the agent cannot proceed.

Constrain scope explicitly. Skills that try to cover everything get applied inconsistently. Define clear boundaries: what this skill covers, what it doesn't, and what adjacent skills handle the rest.

Test against the forgetting curve. Skills are most likely to be skipped when the agent is deep in implementation and eager to deliver. Front-load the most critical constraints in the skill's ## Constraints section — they're read first and remembered longest.

Apply TDD to skill-writing itself.

1. RED: Run the task scenario WITHOUT the skill. Observe how the agent naturally fails.
2. GREEN: Write the minimal skill that addresses those specific failures.
3. REFACTOR: Capture the verbatim excuses the agent generated during baseline testing and build explicit counters into a rationalization prevention table.

Optimize skill descriptions for triggering. The description field in frontmatter determines whether the skill gets invoked. Descriptions that summarize the workflow cause the agent to follow the description instead of reading the full skill. Descriptions should contain triggering conditions only — when should I use this? — not workflow summaries.

Registration

After creating an agent or skill, follow the registration checklist in references/templates.md. For agents, /agent-add performs registration automatically; for skills and slash commands, follow the manual steps. Incomplete registration leaves the system in an inconsistent state.

Documentation Sync Policy

Every change must be reflected in documentation. See the sync policy and source-of-truth table in references/templates.md.

Output

New or updated $PLUGIN/skills/*/SKILL.md file(s) with all registry tables and docs updated. Be concise — confirm what was created/updated and its registration status.

Anti-Patterns