My agent.md to improve LLM-assisted code quality

From FAB's AGENT.MD: > - Avoid magic numbers and strings by extracting recurring or meaningful values into descriptive constants (const) or enums. ---

I've been seeing the same thing with models like GPT5.6 and Opus4.8 in GH Cop CLI. They still introduce magic numbers, and in Scala they often put an entire 10-line Spark expression inside an if condition instead of extracting it into a meaningfully named value to keep "if" readable. I wonder when common sense instructions will be baked into the models.

A bunch of these should be enforce with linting, that way people who still hand-craft code get the same kind of feedback, e.g. Always use {}, even on a one-line "if" statement. & Keep function names short. Less than 30 characters.

Then this one really is a pattern that creates a lot of churn:

- Add a small, to the point, comment to explain what the block does and why. Use examples when possible. Propose ASCII drawings to explain complete systems.

The what _is_ the code.

Since we are sharing our AGENTS.md, I thought I'd share my own, because most of the time, this is pretty much all you need for LLMs to write good code, everything else can be added per project: ---- *Convergence rule* Every substantial task must end in exactly one of three states:

A. Success The intended capability works in the real path and the real motivating case materially improves.

B. Meaningful progression The capability is not complete, but one genuine blocker is removed and the next blocker is isolated with evidence.

C. Honest stop Further work would require overbroad scope expansion, excessive debt, brittle patching, or tangled logic. Stop and report the reason with concrete evidence.

Do not continue producing patches once the work stops converging.

Do not confuse activity with progress. A failed attempt is only acceptable if it leaves behind a narrower problem, stronger evidence, or a justified stop.

Any partial work must leave the codebase in a cleaner, more legible, and more diagnosable state than before. ----

A lot of the article's AGENTS.md just feel like telling the LLM agents either something they already know (for example, most of the time they know to use exhaustive switch/match statements instead of "arrow anti-pattern") or seems actively harmful ("keep function names short" seems arbitrary and may cause the LLMs to write weird abbreviations for functions that are harder to read and review.

A great piece.

I esp liked:

"- Don't touch blocks of code unrelated to the feature you implement. e.g. Don't add comments to a block of code if you did not create it or modify it. As much as possible try to minimize the number of changed lines when implementing a feature."

The feature where you ask the LLM to fix one thing and it fixes three things.

I kept noticing this in diffs.

Just this one line in AGENTS.md has given better results to reduce if not eliminate verbosity and grandeur.

**Always use ASD-STE100 Simplified Technical English

Disclaimer: I saw this listed in some other HN post that I can' locate right away.

This is a problem that people mostly have to solve themselves. Like, I've been working with Claude for almost a year now and I have never once seen it write "Arrow Anti-Pattern" code. That, and much of the rest, would be fluff in my projects. Agent instructions are best learned from experience project-by-project.

I feel like claude.md is like Asimov's laws of robotics. Whatever you write there ends up eventually messing up everything.

I think this is dated. I wonder if the author has tried codex/other harnesses

I didn’t see anything in there instructing the LLM not to generate text about goblins.

I had good results with making it add a few lines with a summary of RFC 2119/8147 keywords (SHALL/MUST...), and then using those, uppercase.

local llm remain more in line like that.

One tactic I’ve found helpful is multi pass quality improvement. First make it work. Then review for guidelines adherence. Loop until satisfied.

I've read a few of these over the years, and none of them seem to be useful. I have three sentences in my custom instructions, and those are basically all useless, too.

Even my second one, "Avoid decorative or section-header comments. Never use `----` or `====` as comment separators. Comments should explain only non-obvious behavior, rationale, constraints, or implementation details." seems to be ignored by models regularly, so I don't see the point.

But this is in my private harness. Perhaps other harnesses have better instruction following. My custom instructions are prepended to my first user message, not set as a system message.

this was what i was doing 3-4 months ago. i just have AI write/update my agents.md file now as i find problems. i also have ai keep a set of design documentation that it can update as it goes too. oh and he should try omp+codex/xhigh, he will probably be less annoyed.

It seems like everyone goes through a detailed AGENTS.md phase.

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Agents.md is such a ridiculous concept, just write good contributing docs and then optionally @ the file in whatever agetn file you use.

That way everyone benefits.