# [An AEO tool that changes what agents receive](https://rebilder.com/solutions/aeo-tool)

> Most AEO tools report a serving-layer problem. This one changes it: scan any URL free, then serve agents clean markdown from two lines of middleware.

- **Updated:** 2026-08-17

There are two kinds of AEO tool: the kind that tells you an answer engine could not use your page, and the kind that fixes it. This is the second kind, and the diagnostic half is free.



## What you get

- Score any URL against a published, deterministic spec
- See the exact markdown an agent receives, side by side with your HTML
- Serve every agent from two lines of middleware, unmetered
- Read the miss log: what agents asked for and did not get

## Diagnosis is cheap; the fix is the product

Nearly every tool in this category is a measurement instrument: it samples answers, or crawls you, and reports a score. That is genuinely useful once, and then it keeps reporting the same score until somebody changes the serving layer. The change is the part that moves the number, so the change is what this is built around.

| Job | What it costs here | What it needs |
| --- | --- | --- |
| Score a URL | Free, no account | A URL |
| See what an agent receives | Free, no account | A URL |
| Serve agents markdown | Free to 1,000 agent visits a month | Two lines of middleware |
| Read the miss log | Included once installed | The gateway running |
| Run it entirely yourself | Free, no account, no telemetry | The open SDK |

## What the tool actually does

It sits in front of your pages and answers content negotiation. A request that asks for markdown gets markdown, built from values you already store; a browser gets your normal page; a search crawler gets canonical HTML. Nothing is generated at request time.

middleware.ts

```ts
import { gateway } from '@rebilder/gateway'

export default gateway({
  source: { kind: 'document', resolve: myPages },
})
```

On the reference product capture, that took a page from 91,226 bytes to 1,315 and moved the first substantive fact from character 23,185 to line 4, with the facts unchanged. There are adapters for common platforms, and the core has no framework dependency.

> **No tier concept at the edge** The SDK has no idea what plan you are on, because it has no concept of a plan. Nothing about your traffic changes what the middleware does, and there is no request-time entitlement lookup to slow it down or to fail closed.

## How to evaluate any AEO tool, including this one

- **Ask what it changes.** If the answer is "it reports", budget for whatever will do the changing.
- **Ask whether the score is deterministic.** A number that moves without your page moving cannot be used to judge a change you made.
- **Ask to see the spec.** [Ours is published](/spec/ars), including the arithmetic, so a score can be checked rather than trusted.
- **Ask what it promises about citations.** Anything guaranteed there is a claim nobody in this market can honour.
- **Ask what it uploads.** Our command-line scanner sends nothing: no scan, no URL, no hostname.

## What this does not do

- It cannot make an assistant mention you. Assistants are not deterministic and no vendor controls their output, so a guaranteed citation is not a thing anyone can sell.
- It does not watch assistants answer questions on your behalf. What it measures is your own server: who asked, what you served, and what you missed.
- It does not write your content. The gateway prints values you already store, and a variant containing a number that came from nowhere is rejected by the validator rather than published.
- It does not audit your competitors. Nothing about a named third party is published without that domain owner’s verified opt-in.

## What does an AEO tool do?

Broadly one of two jobs: measuring whether answer engines can use your pages, or changing what those engines receive. Measurement is the common one and it is worth having; only the second kind moves the score.

## Is there a free AEO tool?

The scan here is free and needs no account, and the gateway SDK is free, unmetered and self-hostable. The paid tier covers hosting and history rather than capability, and the serving path never checks a plan.

## Do I need to change my CMS?

No. It runs as middleware in front of what you already have, with adapters for common platforms and no framework dependency in the core. Your theme, your analytics and your checkout are untouched.

## Will this affect my search rankings?

No. Content negotiation returns the same substance in a different format and search crawlers keep receiving canonical HTML. Serving different prices or availability by requester would be cloaking; a format transformation of identical facts is not.

## Related

- [Answer engine optimization tools: a buyer’s guide](https://rebilder.com/learn/answer-engine-optimization-tools)
- [Answer engine optimization: the method](https://rebilder.com/learn/answer-engine-optimization)
- [What is AEO?](https://rebilder.com/solutions/what-is-aeo)
- [AEO services](https://rebilder.com/solutions/aeo-services)
- [Gateway quickstart](https://rebilder.com/docs/quickstart)