Claude Code

What Claude Code does

Claude Code is a coding agent that runs in the terminal, in an editor extension, or in the browser, and operates on your existing project rather than in a separate sandbox. Given an instruction, it reads relevant files, plans an approach, edits code across multiple files, runs tests and commands, and reports what changed. It reads project instruction files so a repository can carry its own conventions, supports subagents for parallel work, and connects to external systems through the Model Context Protocol. It suits developers working in large or unfamiliar codebases, refactors that touch many files, and debugging where understanding matters more than autocomplete. The limitations are cost and supervision: long agentic sessions consume usage allowances quickly, the agent can take a confidently wrong direction on ambiguous requirements, and every change still needs review, so it rewards developers who can judge output rather than replacing that judgement.

How to use it

Install the command line tool with your package manager, then run it inside a project directory and authenticate with a Claude subscription or an API key. The first session is best spent on a read-only task: ask it to explain how a feature works, so you can see how it searches the codebase before you let it write anything. Add a project instruction file at the repository root describing conventions, build commands and things to avoid, because that file is what stops the agent reinventing your patterns. Work in small, reviewable steps and commit between them, since a large change is hard to unpick. Use plan mode for anything architectural so you approve an approach before edits happen. The two things that trip people up are permissions and context: the agent asks before running commands and that prompt fatigue leads people to approve too broadly, and very long sessions lose earlier detail, so start fresh for a new task.

Best for

• large refactors
• codebase exploration
• debugging
• test generation
• repository automation

Strengths and limitations