Use --allowedTools and --disallowedTools to Control What Claude Can Do

Not every task needs every tool. Sometimes you want Claude to analyze code without editing it, or review files without running commands. The --allowedTools and --disallowedTools flags give you precise control over what Claude can and can't do.

# Read-only mode — Claude can look but not touch
claude --disallowedTools "Edit,Write,Bash"

# Only allow reading and searching — perfect for code audits
claude --allowedTools "Read,Glob,Grep"

# Block command execution but allow file edits
claude --disallowedTools "Bash"

This is especially useful in CI pipelines where you want Claude to perform a specific job without the risk of unintended side effects:

# CI code review — Claude can only read and comment
claude -p --allowedTools "Read,Glob,Grep" \
  "Review this PR for bugs and security issues"

# CI documentation — Claude can read and write docs but not run commands
claude -p --allowedTools "Read,Glob,Grep,Write" \
  "Generate API documentation from the source code"

You can also use glob patterns to allow or block entire groups of MCP tools:

# Allow all tools from a specific MCP server
claude --allowedTools "mcp__myserver__*"

# Block a specific MCP tool you don't want used
claude --disallowedTools "mcp__database__write-query"

A few practical configurations:

• Code review: --allowedTools "Read,Glob,Grep" — analyze without modifying
• Safe refactoring: --disallowedTools "Bash" — edit files but don't run anything
• Documentation: --allowedTools "Read,Glob,Grep,Write" — read code, write docs
• Audit mode: --disallowedTools "Edit,Write,Bash" — pure analysis, zero changes

The safest Claude is one with exactly the permissions it needs — no more, no less.

via Claude Code