In plain words: They tested whether AGENTS.md-style files that describe a code repository actually help coding agents fix real issues, using both generated files and ones developers wrote. Success rates did not improve while costs rose over 20%; only specific coding rules were useful, not general overviews.
Abstract · Evaluating AGENTS.md: Are Repository-Level Context Files Helpful for Coding Agents?
A widespread practice in software development is to tailor coding agents to repositories using context files, such as AGENTS.md. Although this practice is strongly encouraged by agent developers, there is currently no rigorous investigation into whether such context files are actually effective for real-world tasks. In this work, we study this question and evaluate coding agents' task completion performance in two complementary settings: established SWE-bench tasks from popular repositories, with LLM-generated context files, and a novel collection of issues from repositories containing developer-committed context files. Surprisingly, we find that providing context files does not generally improve task success rates, while increasing inference cost by over 20% on average. This observation holds across different LLMs, coding agents, and for both LLM-generated and developer-committed context files. Specifically, we find that while instructions in the context files are well followed by coding agents, repository overviews, although popular and recommended by model providers, are not helpful. We conclude that while context files are useful for specifying non-standard coding practices, any attempts to improve performance should be rigorously evaluated before deployment.
Thibaud Gloaguen, Niels Mündler-Sasahara, Mark Niklas Müller, Veselin Raychev, Martin Vechev
arXiv:2602.11988 · cs.SE, cs.AI · submitted Feb 12, 2026 · updated Sep 29, 2026
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> Surprisingly, we observe that developer-provided files only marginally improve performance compared to omitting them entirely (an increase of 4% on average), while LLM- generated context files have a small negative effect on agent performance (a decrease of 3% on average).
This "surprisingly", and the framing seems misplaced.
For the developer-made ones: 4% improvement is massive! 4% improvement from a simple markdown file means it's a must-have.
> while LLM- generated context files have a small negative effect on agent performance (a decrease of 3% on average)
This should really be "while the prompts used to generate AGENTS files in our dataset..". It's a proxy for prompts, who knows if the ones generated through a better prompt show improvement.
The biggest usecase for AGENTS.md files is domain knowledge that the model is not aware of and cannot instantly infer from the project. That is gained slowly over time from seeing the agents struggle due to this deficiency. Exactly the kind of thing very common in closed-source, yet incredibly rare in public Github projects that have an AGENTS.md file - the huge majority of which are recent small vibecoded projects centered around LLMs. If 4% gains are seen on the latter kind of project, which will have a very mixed quality of AGENTS files in the first place, then for bigger projects with high-quality .md's they're invaluable when working with agents.