[BUG] Agent definition with invalid frontmatter is silently ignored

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?

When the description attribute is missing from an agent's definition frontmatter, it's silently ignored.

What Should Happen?

I see three options:

• Claude should fail to start.
• Show a descriptive error message when an attempt is made to start the agent, or when agents are listed.
• Auto generate the description same as is being done for skills.

Error Messages/Logs

Steps to Reproduce

1. Create an agent definition with just a name: attribute in the frontmatter.
2. List the agents.

The agent is not listed.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.114

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_