Claude SDK Expert

Expert knowledge of Claude Code SDK, tools, and extension development.

Core Tools

File Operations:

// Read files Read({ file_path: '/absolute/path/file.ts' });

// Write files (creates new or overwrites) Write({ file_path: '/absolute/path/file.ts', content: 'export const hello = () => "world";' });

// Edit files (precise replacements) Edit({ file_path: '/absolute/path/file.ts', old_string: 'const x = 1;', new_string: 'const x = 2;' });

Search:

// Find files by pattern Glob({ pattern: '**/*.ts' });

// Search file contents Grep({ pattern: 'TODO', output_mode: 'files_with_matches' });

// Search with context Grep({ pattern: 'function.*export', output_mode: 'content', '-C': 3, // 3 lines before/after '-n': true // Line numbers });

Execution:

// Run commands Bash({ command: 'npm test', description: 'Run test suite' });

// Background processes Bash({ command: 'npm run dev', run_in_background: true });

Agent Tools

Sub-agents:

// Invoke specialized sub-agent Task({ subagent_type: 'plugin:agent-folder:agent-name', prompt: 'Analyze this architecture' });

Skills:

// Activate skill explicitly Skill({ skill: 'skill-name' });

// Or let auto-activation handle it

Commands:

// Execute slash command SlashCommand({ command: '/plugin:command arg1 arg2' });

Plugin Hooks

Available Hook Events:

type HookEvent = | 'PostToolUse' // After tool executes | 'PreToolUse' // Before tool executes | 'PermissionRequest' // User permission dialog | 'Notification' // System notification | 'UserPromptSubmit' // After user submits prompt | 'Stop' // Conversation stopped | 'SubagentStop' // Sub-agent stopped | 'PreCompact' // Before context compaction | 'SessionStart' // Session started | 'SessionEnd'; // Session ended

Hook Configuration:

{ "hooks": { "PostToolUse": [ { "matcher": "TodoWrite", "hooks": [{ "type": "command", "command": "${CLAUDE_PLUGIN_ROOT}/hooks/post-task.sh", "timeout": 10 }] } ] } }

MCP (Model Context Protocol)

Code-First Preferred: Anthropic research shows code execution achieves 98% token reduction vs MCP. Use MCP only for: quick debugging, Claude Desktop integration, or tools with no code equivalent. For automation, CI/CD, and production - write code instead.

MCP Server Integration (when needed):

// Connect to MCP server const mcp = await connectMCP({ name: 'filesystem', transport: 'stdio', command: 'node', args: ['mcp-server-filesystem.js'] });

// Use MCP tools mcp.call('read_file', { path: '/path/to/file' });

Best Practices

Tool Usage:

• Use absolute paths (not relative)

• Handle errors gracefully

• Provide clear descriptions

• Batch independent operations

Performance:

• Minimize tool calls

• Use Grep before Read (search first)

• Parallel independent operations

• Cache results when possible

Security:

• Validate file paths

• Sanitize user input

• No hardcoded secrets

• Use environment variables

Build powerful Claude Code extensions!