---
title: Rebilder Agent Readability Spec (ARS) v0.3.0
description: "The published standard behind Rebilder’s Agent Readability Score: dimensions, weights, scoring arithmetic, crawler policy, and the corpus that enforces it."
canonical_url: https://rebilder.com/spec/ars
---

# [Rebilder Agent Readability Spec \(ARS\) v0.3.0](https://rebilder.com/spec/ars)

> The published, versioned standard behind every Rebilder score: 100 points across seven dimensions, with measured checks separated from heuristic ones and every check carrying its evidence. The full specification text renders at /spec/ars.

- **Description:** The published standard behind Rebilder’s Agent Readability Score: dimensions, weights, scoring arithmetic, crawler policy, and the corpus that enforces it.
- **Author:** Rebilder
- **Organization:** Rebilder

## Principles

The scoring function is pure over a content-addressed evidence bundle: no LLM, no randomness, and no clock in the scoring path. A heuristic value never renders without its label. Ruleset ars-0.3 ships with a public conformance corpus.

## How ARS relates to other readability checks

Other tools also check how well AI agents can read a website. One example is Vercel’s open-source @vercel/agent-readability package. Its audit checks a site against a Vercel guide that its README calls the Agent Readability Spec. That guide is a separate document from ARS, with its own checks.

The two answer different questions. Vercel’s audit looks across a whole site: robots.txt, sitemaps, llms.txt, markdown responses and HTML quality. ARS scores one URL at a time and asks whether the facts that kind of page needs are present, early and cheap to read.

Some results differ by design. Vercel’s audit fails its robots.txt check when GPTBot, ClaudeBot, CCBot or Google-Extended is blocked from the whole site. ARS gives a site that blocks training crawlers but allows AI assistants the same result as a fully open one (§7.4).

A result from one does not convert into a score in the other. You can run both, for example in the same CI job.

Details of @vercel/agent-readability checked on September 28, 2026, version 0.7.0.

## Related

- [Full specification](https://rebilder.com/spec/ars)
- [Scan a URL](https://rebilder.com/scan)
- [Use Rebilder with @vercel/agent-readability](https://rebilder.com/docs/vercel-agent-readability)
- [Compare the two](https://rebilder.com/compare/vercel-agent-readability)