hermes-agent/website/docs/developer-guide/creating-skills.md

---
sidebar_position: 3
title: "Creating Skills"
description: "How to create skills for Hermes Agent — SKILL.md format, guidelines, and publishing"
---

# Creating Skills

Skills are the preferred way to add new capabilities to Hermes Agent. They're easier to create than tools, require no code changes to the agent, and can be shared with the community.

## Should it be a Skill or a Tool?

Make it a **Skill** when:
- The capability can be expressed as instructions + shell commands + existing tools
- It wraps an external CLI or API that the agent can call via `terminal` or `web_extract`
- It doesn't need custom Python integration or API key management baked into the agent
- Examples: arXiv search, git workflows, Docker management, PDF processing, email via CLI tools

Make it a **Tool** when:
- It requires end-to-end integration with API keys, auth flows, or multi-component configuration
- It needs custom processing logic that must execute precisely every time
- It handles binary data, streaming, or real-time events
- Examples: browser automation, TTS, vision analysis

## Skill Directory Structure

Bundled skills live in `skills/` organized by category. Official optional skills use the same structure in `optional-skills/`:

```text
skills/
├── research/
│   └── arxiv/
│       ├── SKILL.md              # Required: main instructions
│       └── scripts/              # Optional: helper scripts
│           └── search_arxiv.py
├── productivity/
│   └── ocr-and-documents/
│       ├── SKILL.md
│       ├── scripts/
│       └── references/
└── ...
```

## SKILL.md Format

```markdown
---
name: my-skill
description: Brief description (shown in skill search results)
version: 1.0.0
author: Your Name
license: MIT
platforms: [macos, linux]          # Optional — restrict to specific OS platforms
                                   #   Valid: macos, linux, windows
                                   #   Omit to load on all platforms (default)
metadata:
  hermes:
    tags: [Category, Subcategory, Keywords]
    related_skills: [other-skill-name]
    requires_toolsets: [web]            # Optional — only show when these toolsets are active
    requires_tools: [web_search]        # Optional — only show when these tools are available
    fallback_for_toolsets: [browser]    # Optional — hide when these toolsets are active
    fallback_for_tools: [browser_navigate]  # Optional — hide when these tools exist
    config:                              # Optional — config.yaml settings the skill needs
      - key: my.setting
        description: "What this setting controls"
        default: "sensible-default"
        prompt: "Display prompt for setup"
required_environment_variables:          # Optional — env vars the skill needs
  - name: MY_API_KEY
    prompt: "Enter your API key"
    help: "Get one at https://example.com"
    required_for: "API access"
---

# Skill Title

Brief intro.

## When to Use
Trigger conditions — when should the agent load this skill?

## Quick Reference
Table of common commands or API calls.

## Procedure
Step-by-step instructions the agent follows.

## Pitfalls
Known failure modes and how to handle them.

## Verification
How the agent confirms it worked.
```

### Platform-Specific Skills

Skills can restrict themselves to specific operating systems using the `platforms` field:

```yaml
platforms: [macos]            # macOS only (e.g., iMessage, Apple Reminders)
platforms: [macos, linux]     # macOS and Linux
platforms: [windows]          # Windows only
```

When set, the skill is automatically hidden from the system prompt, `skills_list()`, and slash commands on incompatible platforms. If omitted or empty, the skill loads on all platforms (backward compatible).

### Conditional Skill Activation

Skills can declare dependencies on specific tools or toolsets. This controls whether the skill appears in the system prompt for a given session.

```yaml
metadata:
  hermes:
    requires_toolsets: [web]           # Hide if the web toolset is NOT active
    requires_tools: [web_search]       # Hide if web_search tool is NOT available
    fallback_for_toolsets: [browser]   # Hide if the browser toolset IS active
    fallback_for_tools: [browser_navigate]  # Hide if browser_navigate IS available
```

| Field | Behavior |
|-------|----------|
| `requires_toolsets` | Skill is **hidden** when ANY listed toolset is **not** available |
| `requires_tools` | Skill is **hidden** when ANY listed tool is **not** available |
| `fallback_for_toolsets` | Skill is **hidden** when ANY listed toolset **is** available |
| `fallback_for_tools` | Skill is **hidden** when ANY listed tool **is** available |

**Use case for `fallback_for_*`:** Create a skill that serves as a workaround when a primary tool isn't available. For example, a `duckduckgo-search` skill with `fallback_for_tools: [web_search]` only shows when the web search tool (which requires an API key) is not configured.

**Use case for `requires_*`:** Create a skill that only makes sense when certain tools are present. For example, a web scraping workflow skill with `requires_toolsets: [web]` won't clutter the prompt when web tools are disabled.

### Environment Variable Requirements

Skills can declare environment variables they need. When a skill is loaded via `skill_view`, its required vars are automatically registered for passthrough into sandboxed execution environments (terminal, execute_code).

```yaml
required_environment_variables:
  - name: TENOR_API_KEY
    prompt: "Tenor API key"               # Shown when prompting user
    help: "Get your key at https://tenor.com"  # Help text or URL
    required_for: "GIF search functionality"   # What needs this var
```

Each entry supports:
- `name` (required) — the environment variable name
- `prompt` (optional) — prompt text when asking the user for the value
- `help` (optional) — help text or URL for obtaining the value
- `required_for` (optional) — describes which feature needs this variable

Users can also manually configure passthrough variables in `config.yaml`:

```yaml
terminal:
  env_passthrough:
    - MY_CUSTOM_VAR
    - ANOTHER_VAR
```

See `skills/apple/` for examples of macOS-only skills.

## Secure Setup on Load

Use `required_environment_variables` when a skill needs an API key or token. Missing values do **not** hide the skill from discovery. Instead, Hermes prompts for them securely when the skill is loaded in the local CLI.

```yaml
required_environment_variables:
  - name: TENOR_API_KEY
    prompt: Tenor API key
    help: Get a key from https://developers.google.com/tenor
    required_for: full functionality
```

The user can skip setup and keep loading the skill. Hermes never exposes the raw secret value to the model. Gateway and messaging sessions show local setup guidance instead of collecting secrets in-band.

:::tip Sandbox Passthrough
When your skill is loaded, any declared `required_environment_variables` that are set are **automatically passed through** to `execute_code` and `terminal` sandboxes — including remote backends like Docker and Modal. Your skill's scripts can access `$TENOR_API_KEY` (or `os.environ["TENOR_API_KEY"]` in Python) without the user needing to configure anything extra. See [Environment Variable Passthrough](/docs/user-guide/security#environment-variable-passthrough) for details.
:::

Legacy `prerequisites.env_vars` remains supported as a backward-compatible alias.

### Config Settings (config.yaml)

Skills can declare non-secret settings that are stored in `config.yaml` under the `skills.config` namespace. Unlike environment variables (which are secrets stored in `.env`), config settings are for paths, preferences, and other non-sensitive values.

```yaml
metadata:
  hermes:
    config:
      - key: myplugin.path
        description: Path to the plugin data directory
        default: "~/myplugin-data"
        prompt: Plugin data directory path
      - key: myplugin.domain
        description: Domain the plugin operates on
        default: ""
        prompt: Plugin domain (e.g., AI/ML research)
```

Each entry supports:
- `key` (required) — dotpath for the setting (e.g., `myplugin.path`)
- `description` (required) — explains what the setting controls
- `default` (optional) — default value if the user doesn't configure it
- `prompt` (optional) — prompt text shown during `hermes config migrate`; falls back to `description`

**How it works:**

1. **Storage:** Values are written to `config.yaml` under `skills.config.<key>`:
   ```yaml
   skills:
     config:
       myplugin:
         path: ~/my-data
   ```

2. **Discovery:** `hermes config migrate` scans all enabled skills, finds unconfigured settings, and prompts the user. Settings also appear in `hermes config show` under "Skill Settings."

3. **Runtime injection:** When a skill loads, its config values are resolved and appended to the skill message:
   ```
   [Skill config (from ~/.hermes/config.yaml):
     myplugin.path = /home/user/my-data
   ]
   ```
   The agent sees the configured values without needing to read `config.yaml` itself.

4. **Manual setup:** Users can also set values directly:
   ```bash
   hermes config set skills.config.myplugin.path ~/my-data
   ```

:::tip When to use which
Use `required_environment_variables` for API keys, tokens, and other **secrets** (stored in `~/.hermes/.env`, never shown to the model). Use `config` for **paths, preferences, and non-sensitive settings** (stored in `config.yaml`, visible in config show).
:::

### Credential File Requirements (OAuth tokens, etc.)

Skills that use OAuth or file-based credentials can declare files that need to be mounted into remote sandboxes. This is for credentials stored as **files** (not env vars) — typically OAuth token files produced by a setup script.

```yaml
required_credential_files:
  - path: google_token.json
    description: Google OAuth2 token (created by setup script)
  - path: google_client_secret.json
    description: Google OAuth2 client credentials
```

Each entry supports:
- `path` (required) — file path relative to `~/.hermes/`
- `description` (optional) — explains what the file is and how it's created

When loaded, Hermes checks if these files exist. Missing files trigger `setup_needed`. Existing files are automatically:
- **Mounted into Docker** containers as read-only bind mounts
- **Synced into Modal** sandboxes (at creation + before each command, so mid-session OAuth works)
- Available on **local** backend without any special handling

:::tip When to use which
Use `required_environment_variables` for simple API keys and tokens (strings stored in `~/.hermes/.env`). Use `required_credential_files` for OAuth token files, client secrets, service account JSON, certificates, or any credential that's a file on disk.
:::

See the `skills/productivity/google-workspace/SKILL.md` for a complete example using both.

## Skill Guidelines

### No External Dependencies

Prefer stdlib Python, curl, and existing Hermes tools (`web_extract`, `terminal`, `read_file`). If a dependency is needed, document installation steps in the skill.

### Progressive Disclosure

Put the most common workflow first. Edge cases and advanced usage go at the bottom. This keeps token usage low for common tasks.

### Include Helper Scripts

For XML/JSON parsing or complex logic, include helper scripts in `scripts/` — don't expect the LLM to write parsers inline every time.

#### Referencing bundled scripts from SKILL.md

When a skill is loaded, the activation message exposes the absolute skill directory as `[Skill directory: /abs/path]` and also substitutes two template tokens anywhere in the SKILL.md body:

| Token | Replaced with |
|---|---|
| `${HERMES_SKILL_DIR}` | Absolute path to the skill's directory |
| `${HERMES_SESSION_ID}` | The active session id (left in place if there is no session) |

So a SKILL.md can tell the agent to run a bundled script directly with:

```markdown
To analyse the input, run:

    node ${HERMES_SKILL_DIR}/scripts/analyse.js <input>
```

The agent sees the substituted absolute path and invokes the `terminal` tool with a ready-to-run command — no path math, no extra `skill_view` round-trip. Disable substitution globally with `skills.template_vars: false` in `config.yaml`.

#### Inline shell snippets (opt-in)

Skills can also embed inline shell snippets written as `` !`cmd` `` in the SKILL.md body. When enabled, each snippet's stdout is inlined into the message before the agent reads it, so skills can inject dynamic context:

```markdown
Current date: !`date -u +%Y-%m-%d`
Git branch: !`git -C ${HERMES_SKILL_DIR} rev-parse --abbrev-ref HEAD`
```

This is **off by default** — any snippet in a SKILL.md runs on the host without approval, so only enable it for skill sources you trust:

```yaml
# config.yaml
skills:
  inline_shell: true
  inline_shell_timeout: 10   # seconds per snippet
```

Snippets run with the skill directory as their working directory, and output is capped at 4000 characters. Failures (timeouts, non-zero exits) show up as a short `[inline-shell error: ...]` marker instead of breaking the whole skill.

### Test It

Run the skill and verify the agent follows the instructions correctly:

```bash
hermes chat --toolsets skills -q "Use the X skill to do Y"
```

## Where Should the Skill Live?

Bundled skills (in `skills/`) ship with every Hermes install. They should be **broadly useful to most users**:

- Document handling, web research, common dev workflows, system administration
- Used regularly by a wide range of people

If your skill is official and useful but not universally needed (e.g., a paid service integration, a heavyweight dependency), put it in **`optional-skills/`** — it ships with the repo, is discoverable via `hermes skills browse` (labeled "official"), and installs with builtin trust.

If your skill is specialized, community-contributed, or niche, it's better suited for a **Skills Hub** — upload it to a registry and share it via `hermes skills install`.

## Publishing Skills

### To the Skills Hub

```bash
hermes skills publish skills/my-skill --to github --repo owner/repo
```

### To a Custom Repository

Add your repo as a tap:

```bash
hermes skills tap add owner/repo
```

Users can then search and install from your repository.

## Security Scanning

All hub-installed skills go through a security scanner that checks for:

- Data exfiltration patterns
- Prompt injection attempts
- Destructive commands
- Shell injection

Trust levels:
- `builtin` — ships with Hermes (always trusted)
- `official` — from `optional-skills/` in the repo (builtin trust, no third-party warning)
- `trusted` — from openai/skills, anthropics/skills
- `community` — non-dangerous findings can be overridden with `--force`; `dangerous` verdicts remain blocked

Hermes can now consume third-party skills from multiple external discovery models:
- direct GitHub identifiers (for example `openai/skills/k8s`)
- `skills.sh` identifiers (for example `skills-sh/vercel-labs/json-render/json-render-react`)
- well-known endpoints served from `/.well-known/skills/index.json`

If you want your skills to be discoverable without a GitHub-specific installer, consider serving them from a well-known endpoint in addition to publishing them in a repo or marketplace.