Agent Skills

A component can embed an Agent Skill — markdown documentation aimed at an LLM agent that’s about to call the component’s tools. The skill is a SKILL.md file (with YAML frontmatter) plus optional supporting files, tar-packed into the act:skill WASM custom section.

Layout

skill/
├── SKILL.md         # required, with frontmatter
├── EXAMPLES.md      # optional
└── references/…     # optional supporting files

SKILL.md

---
name: sqlite
description: Query a SQLite database. Useful for structured tabular data.
metadata:
  act: {}
---

# SQLite Component

Run SQL queries against a database file.

## Tools

### query
Execute a SQL statement. Returns JSON rows.

query(sql: “SELECT * FROM users LIMIT 10”)

Frontmatter fields:

Field	Required	Purpose
name	✓	Slug, matches the component name
description	✓	One-line summary for the agent
metadata.act	✓	Must be {} — signals to skill consumers that this is an ACT skill

Build-time embedding

Nothing in your source code refers to the skill. act-build pack looks for a skill/ directory next to the package manifest, tars it, and writes it into the act:skill custom section — the same way for every language. If the directory is absent, the section is simply omitted.

Run with RUST_LOG=act_build=info to see which sections were written.

Extract

act skill actpkg.dev/library/sqlite:latest -o .agents/skills/sqlite/

Writes the tar contents to the given directory. Agents can then use a skill-add workflow to pick up the documentation without ever running the component.