The Best Free Claude Persona for Code Review
Which free CastMyAgent persona fits code review in Claude, who it suits, and how to set it up in three steps.
Short answer: For code review in Claude, start with Otis, the Senior Code Reviewer persona on CastMyAgent. His pack is built around PR feedback, edge cases, readability, and explaining the reasoning behind every flag. It's free, and it also works in ChatGPT and Gemini.
Who It's For
- Solo developers who want a second pass on a pull request before merging
- Small teams without a dedicated reviewer on every change
- Anyone who wants review comments that explain why, not just what
If you need a reviewer that follows your team's exact style guide line by line, you may get better results writing your own prompt (or adding your guide to a persona). More on that in the FAQ.
Which Personas Fit
Otis, Senior Code Reviewer. The main pick. His listed skills are code review and PR feedback, edge case and failure mode analysis, readability and maintainability critique, security conscious surface level review, and explaining the reasoning behind every flag.
Yuki, Full-Stack Software Engineer. A good fit when the review is really about structure. Yuki's pack covers full stack development, code architecture, code review, performance optimization, and clean code practices.
Naomi, Cybersecurity Analyst. For changes that touch auth, input handling, or infrastructure. Naomi's pack covers threat modeling, vulnerability assessment, security architecture review, incident response, and penetration testing oversight. Otis does a surface level security pass; Naomi goes deeper.
Models It Works With
The packs are plain text, so they work with Claude, ChatGPT, and Gemini. In Claude, a Project's custom instructions or the API system prompt are the most reliable places to put them.
It's Free
All 19 walk-ons on CastMyAgent are free, including Otis, Yuki, and Naomi. The persona text files are MIT licensed.
How to Use It in 3 Steps
- Get the pack. Open Otis's roster page and copy the production file.
- Add it to Claude. Create a Claude Project called "Code Review" and paste the production file into the custom instructions. If you use the API, put it in the
systemparameter. - Give it context and a diff. Paste the diff along with a line about what the change is meant to do, for example:
This PR adds retry logic to the payment webhook handler.
It should retry 3 times with backoff, then log and give up.
Review the diff below.
FAQ
Can a persona replace human code review? No. Treat it as an extra pass that catches things early. A person who knows the system should still approve changes that matter.
Should I write my own code review prompt instead? If your team has strict, specific conventions, a custom prompt built around them may fit better. A middle path is to start with Otis and append your style rules at the end of the production file.
Does it work with Claude Code or other coding tools? Any tool that accepts a system prompt or custom instructions can use the text. Check your tool's docs for where instructions go.
Is there a paid tier I need for this? No. The walk-ons are free.
Browse the full roster at castmyagent.ai.