Read Tool - Claude Code

The Read tool is how Claude pulls file contents into context - the foundation of nearly every real coding task.

What it does

Read takes an absolute path and returns the file contents with line numbers prefixed. It supports offset and limit arguments so Claude can page through huge files without loading them entirely. It also handles images, PDFs, and Jupyter notebooks, returning appropriate representations for each.

When to use it

• Any task where Claude needs to understand existing code.
• Reviewing config files, logs, or test output.
• Grabbing a specific line range from a large file.
• Loading an image or PDF for analysis.

Gotchas

• Empty files return a warning instead of content. Don't panic if you see it.
• Line-numbered output is for reading only - never paste those line numbers into Edit.
• Very large PDFs need a pages parameter. Unbounded PDF reads fail.

Official docs: https://code.claude.com/docs/en/tools-reference.md