Skills

Atomic can create skills. Ask it to build one for your use case.

Skills

Skills are self-contained capability packages that the agent loads on-demand. A skill provides specialized workflows, setup instructions, helper scripts, and reference documentation for specific tasks.

Atomic implements the Agent Skills standard, warning about violations but remaining lenient.

Table of Contents

• Locations
• How Skills Work
• Skill Commands
• Skill Structure
• Frontmatter
• Validation
• Example
• Skill Repositories

Locations

Security: Skills can instruct the model to perform any action and may include executable code the model invokes. Review skill content before use.

Atomic loads skills from:

• Global:
  • ~/.atomic/agent/skills/ (legacy ~/.pi/agent/skills/)
  • ~/.agents/skills/
• Project (only after the project is trusted):
  • .atomic/skills/ (legacy .pi/skills/)
  • .agents/skills/ in cwd and ancestor directories (up to git repo root, or filesystem root when not in a repo)
• Packages: skills/ directories, atomic.skills, or legacy pi.skills entries in package.json
• Settings: skills array with files or directories
• CLI: --skill <path> (repeatable, additive even with --no-skills)

Discovery rules:

• In ~/.atomic/agent/skills/ and .atomic/skills/ (plus legacy ~/.pi/agent/skills/ and .pi/skills/), direct root .md files are discovered as individual skills
• In all skill locations, directories containing SKILL.md are discovered recursively
• In ~/.agents/skills/ and project .agents/skills/, root .md files are ignored

Disable discovery with --no-skills (explicit --skill paths still load).

Using Skills from Other Harnesses

To use skills from Claude Code or OpenAI Codex, add their directories to settings:

{
  "skills": [
    "~/.claude/skills",
    "~/.codex/skills"
  ]
}

For project-level Claude Code skills, add to .atomic/settings.json (legacy .pi/settings.json is also supported):

{
  "skills": ["../.claude/skills"]
}

How Skills Work

1. At startup, Atomic scans skill locations and extracts names and descriptions
2. The system prompt includes available skills in XML format per the specification
3. When a task matches, the agent uses read to load the full SKILL.md (models don’t always do this; use prompting or /skill:name to force it)
4. The agent follows the instructions, using relative paths to reference scripts and assets

This is progressive disclosure: only descriptions are always in context, full instructions load on-demand.

Built-in prompt engineering guidance

The bundled /skill:prompt-engineer creates, optimizes, evaluates, and troubleshoots prompts for GPT-5.6, Claude Opus 5, and Claude Fable 5. It teaches a delete-first workflow: preserve outcomes, safety, permissions, evidence, output, and stopping contracts while removing repetition, generic self-checks, and obsolete process scaffolding. For autonomous prompts it recommends a compact Role · Goal · Success criteria · Constraints · Tools · Output · Stop rules shape, context-dependent tool routing, explicit effort and response-length controls, restrained delegation, grounded progress claims, and documents-first/query-last ordering for long inputs.

The skill no longer recommends response prefilling, which returns an error on Claude 4.6 and later, or visible chain-of-thought as a primary technique. Use explicit output instructions, schemas, tools, or post-processing instead of prefilling. Request conclusions, citations, commands, and observed results rather than reconstructed private reasoning; such requests can trigger Claude Fable 5’s reasoning_extraction safeguard and force a model fallback.

Skill Commands

Skills register as /skill:name commands:

/skill:brave-search           # Load and execute the skill
/skill:pdf-tools extract      # Load skill with arguments

Arguments after the command are appended to the skill content as User: <args>.

Toggle skill commands via /settings in interactive mode or in settings.json:

{
  "enableSkillCommands": true
}

Skill Structure

A skill is a directory with a SKILL.md file. Everything else is freeform.

my-skill/
├── SKILL.md              # Required: frontmatter + instructions
├── scripts/              # Helper scripts
│   └── process.sh
├── references/           # Detailed docs loaded on-demand
│   └── api-reference.md
└── assets/
    └── template.json

SKILL.md Format

---
name: my-skill
description: What this skill does and when to use it. Be specific.
---

# My Skill

## Setup

Run once before first use:
```bash
cd /path/to/skill && bun install
```

## Usage

```bash
./scripts/process.sh <input>
```

Use relative file paths from the skill directory (these are bundled skill files, not docs routes):

See the API reference at `references/api-reference.md` for details.

Keep authored instructions outcome-first and concise. State observable completion and stop conditions, give a short reason for material constraints, and use decision rules for judgment calls instead of ALWAYS/NEVER language. Put detailed or model-specific material in references/ so it loads only when needed. Do not ask models to reproduce private reasoning or repeatedly verify their own work; require evidence or validation results where correctness matters.

Frontmatter

Per the Agent Skills specification:

Field	Required	Description
name	Yes	Max 64 chars. Lowercase a-z, 0-9, hyphens. Must match parent directory.
description	Yes	Max 1024 chars. What the skill does and when to use it.
license	No	License name or reference to bundled file.
compatibility	No	Max 500 chars. Environment requirements.
metadata	No	Arbitrary key-value mapping.
allowed-tools	No	Space-delimited list of pre-approved tools (experimental).
disable-model-invocation	No	When true, skill is hidden from system prompt. Users must use /skill:name.

Name Rules

• 1-64 characters
• Lowercase letters, numbers, hyphens only
• No leading/trailing hyphens
• No consecutive hyphens
• Must match parent directory name

Valid: pdf-processing, data-analysis, code-review Invalid: PDF-Processing, -pdf, pdf--processing

Description Best Practices

The description determines when the agent loads the skill. Be specific.

Good:

description: Extracts text and tables from PDF files, fills PDF forms, and merges multiple PDFs. Use when working with PDF documents.

Poor:

description: Helps with PDFs.

Validation

Atomic validates skills against the Agent Skills standard. Most issues produce warnings but still load the skill:

• Name doesn’t match parent directory
• Name exceeds 64 characters or contains invalid characters
• Name starts/ends with hyphen or has consecutive hyphens
• Description exceeds 1024 characters

Unknown frontmatter fields are ignored.

Exception: Skills with missing description are not loaded.

Name collisions (same name from different locations) warn and keep the first skill found.

Example

brave-search/
├── SKILL.md
├── search.js
└── content.js

SKILL.md:

---
name: brave-search
description: Web search and content extraction via Brave Search API. Use for searching documentation, facts, or any web content.
---

# Brave Search

## Setup

```bash
cd /path/to/brave-search && bun install
```

## Search

```bash
./search.js "query"              # Basic search
./search.js "query" --content    # Include page content
```

## Extract Page Content

```bash
./content.js https://example.com
```

Skill Repositories

• Anthropic Skills - Document processing (docx, pdf, pptx, xlsx), web development
• Pi Skills - Upstream skill examples for web search, browser automation, Google APIs, and transcription