Shell tools let Claude run commands on your machine. Every command is shown to you before execution and requires your approval (unless you’ve enabled auto-approval).
Executes a shell command in your environment. This is the most powerful tool — it can run test suites, build scripts, package managers, git commands, and anything else your shell supports.
Usage pattern:
> Run the test suite
> Install the missing dependency
> Build the project and show me any errors
> Run `npm run lint` and fix the issues it finds
- Running tests:
npm test, pytest, cargo test
- Building:
npm run build, make, gradle build
- Package management:
npm install, pip install, cargo add
- Git operations:
git status, git log, git stash
- File system operations:
mkdir, cp, mv
- Any other shell command
BashTool can execute any shell command. Claude will always show you the command before running it. Review carefully — especially commands that delete files or make network requests.
- First use: Claude shows the command and asks for approval
- You can approve once, approve always for a pattern, or deny
- In plan mode, BashTool commands are planned but not executed until you confirm
On Windows, PowerShellTool runs commands in a PowerShell session instead of bash.
Usage pattern:
> List files in the current directory
> Run the build script
> Evaluate this TypeScript snippet
> Test this regular expression against sample data
For quick one-off evaluations, Claude often uses BashTool with node -e or similar. REPLTool is used when state needs to persist across multiple evaluations.