How to make your AI coding agent stop writing slop

Every AI coding agent I've used shares one habit: it writes the plausible thing. The code compiles. The tests pass. And a senior engineer reviewing it would reach for a red pen. any where a union belongs. Tests that assert on implementation so they survive any refactor. catch (e) {} blocks that quietly swallow production errors. The fix isn't a better model or a cleverer prompt. It's a set of rules at the repo level, written in a format the agent is guaranteed to read. What rules files are Cursor reads .cursor/rules/*.mdc . Claude Code reads CLAUDE.md and AGENTS.md . The .mdc format is plain markdown with YAML frontmatter. Here's the opening of the TypeScript rule file from the AgentForge sample pack: --- description: "Strict TypeScript discipline for production code" globs: "**/*.{ts,tsx}" alwaysApply: true --- Three fields carry the weight. description tells the agent in one sentence what the file is for. globs scopes it, so a TypeScript rule never fires on a Python file. alwaysApply: true loads it into every session. Agents skip a 2,000-line rules file. They read a 40-line one. Write a discipline contract, not a wish list Claude Code follows instructions frighteningly well, and that cuts both ways. Tell it "write good code" and it will be confidently, grammatically wrong. An AGENTS.md contract fixes that. Start with a baseline of rules: think before you act, take small verifiable steps, never claim what you haven't verified, no drive-by refactoring. Then add a verification ladder with six rungs. Does it compile? Does the changed behavior work? Does it break anything adjacent? Does it follow the codebase's conventions? Does it hold at the boundaries? Is it observable in production? The first three are mandatory for every change. Then the failure protocol, which is the line that pays for itself: First failure: fix and re-verify. Second failure: re-derive, your mental model is wrong, form at least two new hypotheses. Third failure: stop, revert to last known-good, d