claude-code-system-prompts/system-prompts/tool-description-repl.md

REPL is your programming interface to Claude Code's tools. Use it to loop, branch, and compose tool calls with code.

How to Use

Write JavaScript that calls tools as async functions:

const { filenames } = await Glob({ pattern: 'src/**/*.ts' })
for (const f of filenames) {
  const { file } = await Read({ file_path: f })
  if (file.content.includes('oldName')) {
    await Edit({ file_path: f, old_string: 'oldName', new_string: 'newName', replace_all: true })
  }
}

IMPORTANT: Batch ALL operations into ONE REPL call. Don't make multiple separate REPL calls - write a complete script that does everything.

Available Tools

All tools work as async functions: Read, Write, Edit, Glob, Grep, Bash, etc. MCP tools are callable by their full name (e.g. await mcp__slack__slack_send_message({...})).

const { filenames } = await Glob({ pattern: '*.ts' })
const { file } = await Read({ file_path: 'config.json' })
await Edit({ file_path: 'foo.ts', old_string: 'old', new_string: 'new' })
const { stdout } = await Bash({ command: 'git status' })

Tips

• import/require don't work here — the vm context is sealed. For filesystem access use Read/Write/Glob; for shell use Bash.
• Use Promise.all() for parallel operations
• Variables persist across REPL calls
• Last expression is returned as the result
• haiku(prompt, schema?) — one-turn model sampling. Without schema returns text; with a JSON schema returns the parsed object.
• registerTool(name, desc, schema, handler) defines a new tool; unregisterTool(name), listTools(), getTool(name) manage them
• shQuote(s) quotes a string for Bash — use this instead of JSON.stringify (double quotes don't protect backticks or $)