gh-basher83-lunar-claude-plugins-devops-python-tools/skills/claude-agent-sdk/references/skills.md

Agent Skills in the SDK

Extend Claude with specialized capabilities using Agent Skills in the Claude Agent SDK

Overview

Agent Skills extend Claude with specialized capabilities that Claude autonomously invokes when relevant. Skills are packaged as SKILL.md files containing instructions, descriptions, and optional supporting resources.

For comprehensive information about Skills, including benefits, architecture, and authoring guidelines, see the Agent Skills overview.

How Skills Work with the SDK

When using the Claude Agent SDK, Skills are:

1. Defined as filesystem artifacts: Created as SKILL.md files in specific directories (.claude/skills/)
2. Loaded from filesystem: Skills are loaded from configured filesystem locations. You must specify settingSources (TypeScript) or setting_sources (Python) to load Skills from the filesystem
3. Automatically discovered: Once filesystem settings are loaded, Skill metadata is discovered at startup from user and project directories; full content loaded when triggered
4. Model-invoked: Claude autonomously chooses when to use them based on context
5. Enabled via allowed_tools: Add "Skill" to your allowed_tools to enable Skills

Unlike subagents (which can be defined programmatically), Skills must be created as filesystem artifacts. The SDK does not provide a programmatic API for registering Skills.

Default behavior: By default, the SDK does not load any filesystem settings. To use Skills, you must explicitly configure settingSources: ['user', 'project'] (TypeScript) or setting_sources=["user", "project"] (Python) in your options.

Using Skills with the SDK

To use Skills with the SDK, you need to:

1. Include "Skill" in your allowed_tools configuration
2. Configure settingSources/setting_sources to load Skills from the filesystem

Once configured, Claude automatically discovers Skills from the specified directories and invokes them when relevant to the user's request.

import asyncio
from claude_agent_sdk import query, ClaudeAgentOptions

async def main():
    options = ClaudeAgentOptions(

cwd="/path/to/project",  # Project with .claude/skills/          cwd="/path/to/project",  # Project with .claude/skills/
          setting_sources=["user", "project"],  # Load Skills from filesystem
          allowed_tools=["Skill", "Read", "Write", "Bash"]  # Enable Skill tool
      )

async for message in query(      async for message in query(
          prompt="Help me process this PDF document",
          options=options
      ):
          print(message)

  asyncio.run(main())

options: { options: { cwd: "/path/to/project", // Project with .claude/skills/ settingSources: ["user", "project"], // Load Skills from filesystem allowedTools: ["Skill", "Read", "Write", "Bash"] // Enable Skill tool } })) { console.log(message); }

## Skill Locations

Skills are loaded from filesystem directories based on your `settingSources`/`setting_sources` configuration:

* **Project Skills** (`.claude/skills/`): Shared with your team via git - loaded when `setting_sources` includes `"project"`
* **User Skills** (`~/.claude/skills/`): Personal Skills across all projects - loaded when `setting_sources` includes `"user"`
* **Plugin Skills**: Bundled with installed Claude Code plugins

## Creating Skills

Skills are defined as directories containing a `SKILL.md` file with YAML frontmatter and Markdown content. The `description` field determines when Claude invokes your Skill.

**Example directory structure**:

```bash  theme={null}
.claude/skills/processing-pdfs/
└── SKILL.md

For complete guidance on creating Skills, including SKILL.md structure, multi-file Skills, and examples, see:

• Agent Skills in Claude Code: Complete guide with examples
• Agent Skills Best Practices: Authoring guidelines and naming conventions

Tool Restrictions

The allowed-tools frontmatter field in SKILL.md is only supported when using Claude Code CLI directly. It does not apply when using Skills through the SDK.

When using the SDK, control tool access through the main allowedTools option in your query configuration.

To restrict tools for Skills in SDK applications, use the allowedTools option:

Import statements from the first example are assumed in the following code snippets.

options = ClaudeAgentOptions(
    setting_sources=["user", "project"],  # Load Skills from filesystem

allowed_tools=["Skill", "Read", "Grep", "Glob"]  # Restricted toolset      allowed_tools=["Skill", "Read", "Grep", "Glob"]  # Restricted toolset
  )

  async for message in query(
      prompt="Analyze the codebase structure",
```python
options=options      options=options
  ):
      print(message)

options: { options: { settingSources: ["user", "project"], // Load Skills from filesystem allowedTools: ["Skill", "Read", "Grep", "Glob"] // Restricted toolset } })) { console.log(message); }

## Discovering Available Skills

To see which Skills are available in your SDK application, simply ask Claude:

```python Python theme={null}
options = ClaudeAgentOptions(
    setting_sources=["user", "project"],  # Load Skills from filesystem
```python
allowed_tools=["Skill"]      allowed_tools=["Skill"]
)

async for message in query(
    prompt="What Skills are available?",
```python
options=options      options=options
):
    print(message)

options: { options: { settingSources: ["user", "project"], // Load Skills from filesystem allowedTools: ["Skill"] } })) { console.log(message); }

Claude will list the available Skills based on your current working directory and installed plugins.

## Testing Skills

Test Skills by asking questions that match their descriptions:

```python Python theme={null}
options = ClaudeAgentOptions(
    cwd="/path/to/project",
```python
setting_sources=["user", "project"],  # Load Skills from filesystem      setting_sources=["user", "project"],  # Load Skills from filesystem
    allowed_tools=["Skill", "Read", "Bash"]
)

async for message in query(
    prompt="Extract text from invoice.pdf",
```python
options=options      options=options
):
    print(message)

options: { options: { cwd: "/path/to/project", settingSources: ["user", "project"], // Load Skills from filesystem allowedTools: ["Skill", "Read", "Bash"] } })) { console.log(message); }

Claude automatically invokes the relevant Skill if the description matches your request.

## Troubleshooting

### Skills Not Found

**Check settingSources configuration**: Skills are only loaded when you explicitly configure `settingSources`/`setting_sources`. This is the most common issue:

```python Python theme={null}

## Wrong - Skills won't be loaded

options = ClaudeAgentOptions(
    allowed_tools=["Skill"]
)

## Correct - Skills will be loaded

options = ClaudeAgentOptions(
    setting_sources=["user", "project"],  # Required to load Skills
```python
allowed_tools=["Skill"]      allowed_tools=["Skill"]
)

allowedTools: ["Skill"] allowedTools: ["Skill"] };

For more details on `settingSources`/`setting_sources`, see the [TypeScript SDK reference](/en/api/agent-sdk/typescript#settingsource) or [Python SDK reference](/en/api/agent-sdk/python#settingsource).

**Check working directory**: The SDK loads Skills relative to the `cwd` option. Ensure it points to a directory containing `.claude/skills/`:

```python Python theme={null}

## Ensure your cwd points to the directory containing .claude/skills/

options = ClaudeAgentOptions(
    cwd="/path/to/project",  # Must contain .claude/skills/
```python
setting_sources=["user", "project"],  # Required to load Skills      setting_sources=["user", "project"],  # Required to load Skills
    allowed_tools=["Skill"]
)

settingSources: ["user", "project"], // Required to load Skills settingSources: ["user", "project"], // Required to load Skills allowedTools: ["Skill"] };

See the "Using Skills with the SDK" section above for the complete pattern.

**Verify filesystem location**:

```bash  theme={null}

## Check project Skills

ls .claude/skills/*/SKILL.md

## Check personal Skills

ls ~/.claude/skills/*/SKILL.md

Skill Not Being Used

Check the Skill tool is enabled: Confirm "Skill" is in your allowedTools.

Check the description: Ensure it's specific and includes relevant keywords. See Agent Skills Best Practices for guidance on writing effective descriptions.

Additional Troubleshooting

For general Skills troubleshooting (YAML syntax, debugging, etc.), see the Claude Code Skills troubleshooting section.

Related Documentation

Skills Guides

• Agent Skills in Claude Code: Complete Skills guide with creation, examples, and troubleshooting
• Agent Skills Overview: Conceptual overview, benefits, and architecture
• Agent Skills Best Practices: Authoring guidelines for effective Skills
• Agent Skills Cookbook: Example Skills and templates

SDK Resources

• Subagents in the SDK: Similar filesystem-based agents with programmatic options
• Slash Commands in the SDK: User-invoked commands
• SDK Overview: General SDK concepts
• TypeScript SDK Reference: Complete API documentation
• Python SDK Reference: Complete API documentation