# What changed (`mttr_changes`)

Updated October 24, 2026.

## What does mttr_changes do?

What the latest read of a site changed against the one before it: the score, rules now passing, rules newly failing, and pages added and removed. Any key may make this call, on any public site.

Who may call it: Any key.

## When to use it

- A read you asked for is done.
- A score moved and you want to know why.

## What you ask

You might say: “What changed on example.com since the last read?”

```
mttr_changes({ site: "example.com" })
```

| Argument | Type | Needed | What it is |
| --- | --- | --- | --- |
| `site` | Text | Yes | The site, as a domain such as example.com. |

## What comes back

- The score then and now.
- Rules now passing and rules newly failing.
- Pages added and removed.
- For a site that sends its own visit counts, its visits in the week before the read and the week since, so a fix can be judged by what followed it.

A sample, with made-up sites and figures:

Score 64 to 72. 3 pages added, 1 removed.

- Now passing: Show sources on guides
- Now passing: Add a tap-to-call link
- Newly failing: Fix description lengths

A score says pages are well formed. It does not say an assistant cites the site.

## Over HTTP

```
curl "https://mttr.si/api/v1/sites/example.com/changes" \
  -H "Authorization: Bearer $MTTR_KEY"
```

## When it fails

| When | Status | What to do |
| --- | --- | --- |
| Your assistant has no key yet | 401 over MCP | Sign up with `mttr_signup`, then connect again with the key it gives. |
| mttr has no public report of the site yet | 404 | Ask for a read with `mttr_rescan`, then watch it with `mttr_job`. |

## Sources

- [Model Context Protocol: tools](https://modelcontextprotocol.io/specification/2025-06-18/server/tools), Model Context Protocol: How an assistant calls a tool.

The call in full: [mttr_changes in the API reference](https://mttr.si/docs/reference#mttr_changes).

## Goes with

- [Read it again](https://mttr.si/docs/tools/rescan.md)
- [What happened lately](https://mttr.si/docs/tools/events.md)