287 lines
10 KiB
Markdown
287 lines
10 KiB
Markdown
# Agent Skills in the SDK
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> Extend Claude with specialized capabilities using Agent Skills in the Claude Agent SDK
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## Overview
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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.
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For comprehensive information about Skills, including benefits, architecture, and authoring guidelines, see the [Agent Skills overview](/en/docs/agents-and-tools/agent-skills/overview).
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## How Skills Work with the SDK
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When using the Claude Agent SDK, Skills are:
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1. **Defined as filesystem artifacts**: Created as `SKILL.md` files in specific directories (`.claude/skills/`)
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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
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3. **Automatically discovered**: Once filesystem settings are loaded, Skill metadata is discovered at startup from user and project directories; full content loaded when triggered
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4. **Model-invoked**: Claude autonomously chooses when to use them based on context
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5. **Enabled via allowed\_tools**: Add `"Skill"` to your `allowed_tools` to enable Skills
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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.
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**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.
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## Using Skills with the SDK
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To use Skills with the SDK, you need to:
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1. Include `"Skill"` in your `allowed_tools` configuration
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2. Configure `settingSources`/`setting_sources` to load Skills from the filesystem
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Once configured, Claude automatically discovers Skills from the specified directories and invokes them when relevant to the user's request.
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```python Python theme={null}
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import asyncio
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from claude_agent_sdk import query, ClaudeAgentOptions
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async def main():
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options = ClaudeAgentOptions(
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```
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```python
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cwd="/path/to/project", # Project with .claude/skills/ cwd="/path/to/project", # Project with .claude/skills/
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setting_sources=["user", "project"], # Load Skills from filesystem
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allowed_tools=["Skill", "Read", "Write", "Bash"] # Enable Skill tool
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)
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```
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```python
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async for message in query( async for message in query(
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prompt="Help me process this PDF document",
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options=options
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):
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print(message)
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asyncio.run(main())
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```
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options: { options: {
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cwd: "/path/to/project", // Project with .claude/skills/
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settingSources: ["user", "project"], // Load Skills from filesystem
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allowedTools: ["Skill", "Read", "Write", "Bash"] // Enable Skill tool
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}
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})) {
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console.log(message);
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}
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```text
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## Skill Locations
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Skills are loaded from filesystem directories based on your `settingSources`/`setting_sources` configuration:
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* **Project Skills** (`.claude/skills/`): Shared with your team via git - loaded when `setting_sources` includes `"project"`
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* **User Skills** (`~/.claude/skills/`): Personal Skills across all projects - loaded when `setting_sources` includes `"user"`
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* **Plugin Skills**: Bundled with installed Claude Code plugins
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## Creating Skills
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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.
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**Example directory structure**:
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```bash theme={null}
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.claude/skills/processing-pdfs/
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└── SKILL.md
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```
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For complete guidance on creating Skills, including SKILL.md structure, multi-file Skills, and examples, see:
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* [Agent Skills in Claude Code](/en/docs/claude-code/skills): Complete guide with examples
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* [Agent Skills Best Practices](/en/docs/agents-and-tools/agent-skills/best-practices): Authoring guidelines and naming conventions
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## Tool Restrictions
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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**.
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When using the SDK, control tool access through the main `allowedTools` option in your query configuration.
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To restrict tools for Skills in SDK applications, use the `allowedTools` option:
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Import statements from the first example are assumed in the following code snippets.
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```python Python theme={null}
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options = ClaudeAgentOptions(
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setting_sources=["user", "project"], # Load Skills from filesystem
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```
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```python
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allowed_tools=["Skill", "Read", "Grep", "Glob"] # Restricted toolset allowed_tools=["Skill", "Read", "Grep", "Glob"] # Restricted toolset
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)
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async for message in query(
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prompt="Analyze the codebase structure",
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```python
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options=options options=options
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):
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print(message)
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```
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options: { options: {
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settingSources: ["user", "project"], // Load Skills from filesystem
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allowedTools: ["Skill", "Read", "Grep", "Glob"] // Restricted toolset
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}
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})) {
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console.log(message);
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}
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```text
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## Discovering Available Skills
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To see which Skills are available in your SDK application, simply ask Claude:
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```python Python theme={null}
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options = ClaudeAgentOptions(
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setting_sources=["user", "project"], # Load Skills from filesystem
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```python
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allowed_tools=["Skill"] allowed_tools=["Skill"]
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)
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async for message in query(
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prompt="What Skills are available?",
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```python
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options=options options=options
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):
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print(message)
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```
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options: { options: {
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settingSources: ["user", "project"], // Load Skills from filesystem
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allowedTools: ["Skill"]
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}
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})) {
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console.log(message);
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}
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```text
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Claude will list the available Skills based on your current working directory and installed plugins.
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## Testing Skills
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Test Skills by asking questions that match their descriptions:
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```python Python theme={null}
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options = ClaudeAgentOptions(
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cwd="/path/to/project",
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```python
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setting_sources=["user", "project"], # Load Skills from filesystem setting_sources=["user", "project"], # Load Skills from filesystem
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allowed_tools=["Skill", "Read", "Bash"]
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)
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async for message in query(
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prompt="Extract text from invoice.pdf",
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```python
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options=options options=options
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):
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print(message)
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```
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options: { options: {
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cwd: "/path/to/project",
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settingSources: ["user", "project"], // Load Skills from filesystem
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allowedTools: ["Skill", "Read", "Bash"]
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}
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})) {
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console.log(message);
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}
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```text
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Claude automatically invokes the relevant Skill if the description matches your request.
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## Troubleshooting
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### Skills Not Found
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**Check settingSources configuration**: Skills are only loaded when you explicitly configure `settingSources`/`setting_sources`. This is the most common issue:
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```python Python theme={null}
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## Wrong - Skills won't be loaded
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options = ClaudeAgentOptions(
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allowed_tools=["Skill"]
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)
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## Correct - Skills will be loaded
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options = ClaudeAgentOptions(
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setting_sources=["user", "project"], # Required to load Skills
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```python
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allowed_tools=["Skill"] allowed_tools=["Skill"]
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)
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```
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allowedTools: ["Skill"] allowedTools: ["Skill"]
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};
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```text
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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).
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**Check working directory**: The SDK loads Skills relative to the `cwd` option. Ensure it points to a directory containing `.claude/skills/`:
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```python Python theme={null}
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## Ensure your cwd points to the directory containing .claude/skills/
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options = ClaudeAgentOptions(
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cwd="/path/to/project", # Must contain .claude/skills/
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```python
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setting_sources=["user", "project"], # Required to load Skills setting_sources=["user", "project"], # Required to load Skills
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allowed_tools=["Skill"]
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)
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```
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settingSources: ["user", "project"], // Required to load Skills settingSources: ["user", "project"], // Required to load Skills
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allowedTools: ["Skill"]
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};
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```text
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See the "Using Skills with the SDK" section above for the complete pattern.
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**Verify filesystem location**:
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```bash theme={null}
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## Check project Skills
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ls .claude/skills/*/SKILL.md
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## Check personal Skills
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ls ~/.claude/skills/*/SKILL.md
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```
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### Skill Not Being Used
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**Check the Skill tool is enabled**: Confirm `"Skill"` is in your `allowedTools`.
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**Check the description**: Ensure it's specific and includes relevant keywords. See [Agent Skills Best Practices](/en/docs/agents-and-tools/agent-skills/best-practices#writing-effective-descriptions) for guidance on writing effective descriptions.
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### Additional Troubleshooting
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For general Skills troubleshooting (YAML syntax, debugging, etc.), see the [Claude Code Skills troubleshooting section](/en/docs/claude-code/skills#troubleshooting).
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## Related Documentation
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### Skills Guides
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* [Agent Skills in Claude Code](/en/docs/claude-code/skills): Complete Skills guide with creation, examples, and troubleshooting
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* [Agent Skills Overview](/en/docs/agents-and-tools/agent-skills/overview): Conceptual overview, benefits, and architecture
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* [Agent Skills Best Practices](/en/docs/agents-and-tools/agent-skills/best-practices): Authoring guidelines for effective Skills
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* [Agent Skills Cookbook](https://github.com/anthropics/claude-cookbooks/tree/main/skills): Example Skills and templates
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### SDK Resources
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* [Subagents in the SDK](/en/api/agent-sdk/subagents): Similar filesystem-based agents with programmatic options
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* [Slash Commands in the SDK](/en/api/agent-sdk/slash-commands): User-invoked commands
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* [SDK Overview](/en/api/agent-sdk/overview): General SDK concepts
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* [TypeScript SDK Reference](/en/api/agent-sdk/typescript): Complete API documentation
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* [Python SDK Reference](/en/api/agent-sdk/python): Complete API documentation
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