guardrails.txt
My app exposes a model to users here: <describe the feature>

Add the practical protections:
- Input length cap, and a rate limit per user and per IP.
- A hard spend cap across all users that fails closed, with an alert
  before it's reached.
- Treat model output as untrusted: never render it as HTML, never
  execute it, never put it into a query.
- If user content is passed into the prompt, structure it so
  instructions inside that content aren't followed. Show me how.
- Log the prompt and response for anything that errors or gets
  flagged, with personal data excluded.

Tell me what someone would try first to abuse this, and which
protection stops it.

Model output is user input from somewhere else. If you render it as HTML, you've built a cross-site scripting hole with extra steps.