Ponytail in OpenCode: The Agent That Writes Less Code

The problem: agents write too much

Example: “Email validator” → 500 lines, 3 packages, long comments. They write a lot, but not always well.

What is Ponytail

Ponytail is a personality plugin for your code agent. It is not a new model. It is a set of rules and skills. It teaches the agent to think like a “lazy senior developer”: write one line and it works.

How Ponytail works

The agent asks itself:

• Does the standard library already do this?
• Is there already a native function for this?
• Can an installed dependency solve this?
• Can I do it in one line?
• Do I really need this?

It prefers simplicity: less packages, less functions, less files.

Benchmark results

• 80–94% less code.
• 47–77% less cost.
• 3–6x faster.
• Same model, same tests, same success rate.

Who is Ponytail for

• Developers who want cleaner and cheaper code.
• Teams with over-engineering and unnecessary packages.
• Teachers who show how to ask: “do I really need this?”.
• AI enthusiasts who want more “senior” agents.

Ponytail commands and levels

Commands: /ponytail, /ponytail-review, /ponytail-audit, /ponytail-debt, /ponytail-help.

Levels: lite, full, ultra, off. Default: full.

Practice walkthrough

1. Create a directory for the project and create opencode.json with just {}.
2. Open OpenCode and ask: “Make me an email validator in JS that I can run with NodeJS”.
3. See how many lines it writes and notice the unnecessary things.
4. Clone Ponytail:

   git clone https://github.com/DietrichGebert/ponytail.git
   

5. Add to opencode.json:

   {
     "$schema": "https://opencode.ai/config.json",
     "plugin": ["../ponytail/.opencode/plugins/ponytail.mjs"]
   }
   

6. Open OpenCode and activate Ponytail: /ponytail full.
7. Ask: “Create a JS script in a file called email-validator-ponytail.js to validate emails”.
8. Notice how the code is shorter and stays focused on what you asked.
9. Try the audit: /ponytail-audit and fix the points you want.

Video

In the following video you can see the complete process (Spanish audio).