Cursor Rules: How to Stop Your AI Agent From Writing Slop

You just installed Cursor, opened a TypeScript file, and asked the agent to fix a bug. Ten seconds later it handed you a type SomeType = any and a @ts-ignore above the line that wouldn't compile. This is the moment most developers discover that AI coding agents are powerful but undisciplined. The fix isn't a better model. It's rules. Most AI coding agent best practices boil down to a single idea: tell the agent what good looks like before it starts typing. Cursor lets you define rules files in .cursor/rules/ that load alongside your project context and tell the agent how to behave. Claude Code has its own rules system, Windsurf has a rules directory, Copilot reads .github/copilot-instructions.md . Learn to configure cursor rules properly and your agent starts behaving like a careful senior engineer instead of an eager intern. What cursor rules files are Cursor rules are markdown files with a .mdc extension stored in .cursor/rules/ at your project root. Each file is a set of instructions the agent reads before it starts working. When a rule's conditions match the file being edited, the instruction is injected into the model's context window. A cursor rules file has two parts: a YAML frontmatter block between --- markers, and a markdown body with the actual instructions. How to configure cursor rules: the frontmatter fields Three fields matter. description (required). A short summary of what the rule enforces. Cursor surfaces this when you toggle rules, so make it specific. globs (optional). File patterns the rule applies to. Without globs, the rule applies to everything, which wastes context and creates conflicts. alwaysApply (optional). Set to true for rules that should load in every session, regardless of the files involved. Leave it false for rules that only trigger when matching files are touched. Real example: --- description : Enforce strict TypeScript, no any, no ts-ignore globs : ** /*.{ts,tsx} alwaysApply : false --- # Strict TypeScript ## Context This codeb