Write rules as operational constraints: when using MCP

Tip: Rules are not a style essay

Say what the agent must never do: no seed, keep published_at filters, no JS build. Review the tool list after connect and pin server versions.

---
description: lexprog invariants
globs: src/**/*.rs
---
Never run cargo run --bin seed.

Gotcha: A rule that restates Rust book (when using mcp)

The model already knows Rust. Spend tokens on this repo's footguns. A filesystem server rooted at / is a data leak.

# What is ownership?

Source: https://docs.cursor.com/context/rules