[BUG] Update `Fetch` tool docstring to indicate that it cannot open `localhost` URLs

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude often defaults to its internal Fetch tool when loading URLs, but when the URLs are served on localhost, it fails every time. Update the documentation that is passed to the agent's context to notify it that it cannot load URLs from localhost and should instead use an alternate bash command like curl.

What Should Happen?

Claude should know to not attempt to load local URLs using the fetch tool.

Error Messages/Logs

Steps to Reproduce

Ask Claude to load a URL served on localhost.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

1.0.115 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_