# Agent Skills

> Create, manage, and share Skills to extend HopCode's capabilities.

This guide shows you how to create, use, and manage Agent Skills in **HopCode**. Skills are modular capabilities that extend the model's effectiveness through organized folders containing instructions (and optionally scripts/resources).

## Prerequisites

- HopCode (recent version)
- Basic familiarity with HopCode ([Quickstart](../quickstart.md))

## What are Agent Skills?

Agent Skills package expertise into discoverable capabilities. Each Skill consists of a `SKILL.md` file with instructions that the model can load when relevant, plus optional supporting files like scripts and templates.

### How Skills are invoked

Skills are **model-invoked** — the model autonomously decides when to use them based on your request and the Skill's description. This is different from slash commands, which are **user-invoked** (you explicitly type `/command`).

If you want to invoke a Skill explicitly, use the `/skills` slash command:

```bash
/skills <skill-name>
```

Use autocomplete to browse available Skills and descriptions.

### Benefits

- Extend HopCode for your workflows
- Share expertise across your team via git
- Reduce repetitive prompting
- Compose multiple Skills for complex tasks

## Create a Skill

Skills are stored as directories containing a `SKILL.md` file.

### Personal Skills

Personal Skills are available across all your projects. Store them in `~/.hopcode/skills/`:

```bash
mkdir -p ~/.hopcode/skills/my-skill-name
```

Use personal Skills for:

- Your individual workflows and preferences
- Skills you're developing
- Personal productivity helpers

### Project Skills

Project Skills are shared with your team. Store them in `.hopcode/skills/` within your project:

```bash
mkdir -p .hopcode/skills/my-skill-name
```

Use project Skills for:

- Team workflows and conventions
- Project-specific expertise
- Shared utilities and scripts

Project Skills can be checked into git and automatically become available to teammates.

## Write `SKILL.md`

Create a `SKILL.md` file with YAML frontmatter and Markdown content:

```yaml
---
name: your-skill-name
description: Brief description of what this Skill does and when to use it
priority: 10
---

# Your Skill Name

## Instructions
Provide clear, step-by-step guidance for HopCode.

## Examples
Show concrete examples of using this Skill.
```

### Field requirements

HopCode currently validates that:

- `name` is a non-empty string matching `/^[\p{L}\p{N}_:.-]+$/u` — Unicode letters and digits (CJK / Cyrillic / accented Latin all OK), plus `_`, `:`, `.`, `-`. Whitespace, slashes, brackets and other structurally unsafe characters are rejected at parse time.
- `description` is a non-empty string
- `priority` is optional. When present, it must be a finite number. Higher values sort earlier in the `/skills` listing only — slash-command completion (typing `/`) and the `/help` custom commands view stay alphabetical, so a high-priority Skill never reorders built-in commands. Omitted or invalid values are treated as unset, which behaves like `0`.

Recommended conventions:

- Prefer lowercase ASCII with hyphens for shareable names (e.g. `tsx-helper`)
- Make `description` specific: include both **what** the Skill does and **when** to use it (key words users will naturally mention)
- Use `priority` sparingly for Skills that should reliably appear before the default alphabetical order in `/skills`. Negative priorities are allowed and sort below unset Skills.

### Optional: gate a Skill on file paths (`paths:`)

For Skills that only matter to specific parts of a codebase, add a `paths:` list of glob patterns. The Skill stays out of the model's available-skills listing until a tool call touches a matching file:

```yaml
---
name: tsx-helper
description: React TSX component helper
paths:
  - 'src/**/*.tsx'
  - 'packages/*/src/**/*.tsx'
---
```

Notes:

- Globs are matched relative to the project root with [picomatch](https://github.com/micromatch/picomatch); files outside the project root never trigger activation.
- A path-gated Skill **stays activated for the rest of the session** once a matching file is touched. A new session, or a `refreshCache` triggered by editing any Skill file, resets activations.
- `paths:` only gates **model** discovery, and only at the SkillTool listing level. Unless `user-invocable: false` is set, you can always invoke a path-gated Skill yourself via `/<skill-name>` or the `/skills` picker — that user path runs the Skill body regardless of activation state. The model side, however, stays gated until a matching file is touched: a slash invocation does **not** unlock model-side activation, so if you want the model to chain off your invocation (call `Skill { skill: ... }` itself), also access a file matching the skill's `paths:` first.
- Combining `paths:` with `disable-model-invocation: true` is allowed but the gate has no effect — the Skill is hidden from the model regardless, so path activation never advertises it.

### Optional: control user and model invocation

Skills are user-invocable by default. To hide a Skill from direct slash-command use while keeping it available for model invocation, set `user-invocable: false`:

```yaml
---
name: model-only-helper
description: Helper the model can call when appropriate
user-invocable: false
---
```

This removes the Skill from `/<skill-name>` invocation and `/skills` picker results. It does not hide the Skill from the model.

To hide a Skill from model invocation while keeping direct user invocation available, set `disable-model-invocation: true`:

```yaml
---
name: manual-helper
description: Helper you invoke manually
disable-model-invocation: true
---
```

You can combine both fields, but then the Skill is not reachable through the normal user or model invocation paths.

## Add supporting files

Create additional files alongside `SKILL.md`:

```text
my-skill/
├── SKILL.md (required)
├── reference.md (optional documentation)
├── examples.md (optional examples)
├── scripts/
│   └── helper.py (optional utility)
└── templates/
    └── template.txt (optional template)
```

Reference these files from `SKILL.md`:

````markdown
For advanced usage, see [reference.md](reference.md).

Run the helper script:

```bash
python scripts/helper.py input.txt
```
````

## View available Skills

HopCode discovers Skills from:

- Personal Skills: `~/.hopcode/skills/`
- Project Skills: `.hopcode/skills/`
- Extension Skills: Skills provided by installed extensions

### Extension Skills

Extensions can provide custom skills that become available when the extension is enabled. These skills are stored in the extension's `skills/` directory and follow the same format as personal and project skills.

Extension skills are automatically discovered and loaded when the extension is installed and enabled.

To see which extensions provide skills, check the extension's `hopcode-extension.json` file for a `skills` field.

To view available Skills, ask HopCode directly:

```text
What Skills are available?
```

> **Heads up — model vs. user view.** Asking the model only surfaces Skills the model can currently see. If a Skill uses `paths:` (see "Optional: gate a Skill on file paths" above), it stays out of that listing until a matching file has been touched. The `/skills` slash command shows Skills you can invoke directly; Skills with `user-invocable: false` remain visible on disk and may still be visible to the model.

Or browse the user-invocable list with the slash command (including path-gated Skills that have not activated yet):

```text
/skills
```

Or inspect the filesystem:

```bash
# List personal Skills
ls ~/.hopcode/skills/

# List project Skills (if in a project directory)
ls .hopcode/skills/

# View a specific Skill's content
cat ~/.hopcode/skills/my-skill/SKILL.md
```

## Test a Skill

After creating a Skill, test it by asking questions that match your description.

Example: if your description mentions "PDF files":

```text
Can you help me extract text from this PDF?
```

The model autonomously decides to use your Skill if it matches the request — you don't need to explicitly invoke it.

## Debug a Skill

If HopCode doesn't use your Skill, check these common issues:

### Make the description specific

Too vague:

```yaml
description: Helps with documents
```

Specific:

```yaml
description: Extract text and tables from PDF files, fill forms, merge documents. Use when working with PDFs, forms, or document extraction.
```

### Verify file path

- Personal Skills: `~/.hopcode/skills/<skill-name>/SKILL.md`
- Project Skills: `.hopcode/skills/<skill-name>/SKILL.md`

```bash
# Personal
ls ~/.hopcode/skills/my-skill/SKILL.md

# Project
ls .hopcode/skills/my-skill/SKILL.md
```

### Check YAML syntax

Invalid YAML prevents the Skill metadata from loading correctly.

```bash
cat SKILL.md | head -n 15
```

Ensure:

- Opening `---` on line 1
- Closing `---` before Markdown content
- Valid YAML syntax (no tabs, correct indentation)

### View errors

Run HopCode with debug mode to see Skill loading errors:

```bash
hopcode --debug
```

## Share Skills with your team

You can share Skills through project repositories:

1. Add the Skill under `.hopcode/skills/`
2. Commit and push
3. Teammates pull the changes

```bash
git add .hopcode/skills/
git commit -m "Add team Skill for PDF processing"
git push
```

## Update a Skill

Edit `SKILL.md` directly:

```bash
# Personal Skill
code ~/.hopcode/skills/my-skill/SKILL.md

# Project Skill
code .hopcode/skills/my-skill/SKILL.md
```

Changes take effect the next time you start HopCode. If HopCode is already running, restart it to load the updates.

## Remove a Skill

Delete the Skill directory:

```bash
# Personal
rm -rf ~/.hopcode/skills/my-skill

# Project
rm -rf .hopcode/skills/my-skill
git commit -m "Remove unused Skill"
```

## Best practices

### Keep Skills focused

One Skill should address one capability:

- Focused: "PDF form filling", "Excel analysis", "Git commit messages"
- Too broad: "Document processing" (split into smaller Skills)

### Write clear descriptions

Help the model discover when to use Skills by including specific triggers:

```yaml
description: Analyze Excel spreadsheets, create pivot tables, and generate charts. Use when working with Excel files, spreadsheets, or .xlsx data.
```

### Test with your team

- Does the Skill activate when expected?
- Are the instructions clear?
- Are there missing examples or edge cases?