# get_evidence_for_change

> Retrieves a saved comparison result by its evidence ID, with the source data versions and evidence rows it used. It also reports if the underlying data has…

**Source:** [https://queryhippo.com/docs/tools/get_evidence_for_change](https://queryhippo.com/docs/tools/get_evidence_for_change)

What exact data was a saved comparison based on, and is it still current?

- Read-only
- No external calls

## When to use it

Retrieves a saved comparison result by its evidence ID, with the source data versions and evidence rows it used. It also reports if the underlying data has changed since.

## Ask your AI

- Show me the evidence behind that comparison.
- Is the evidence for my last comparison still current?

## Parameters

| Name | Type | Details | What it means |
| --- | --- | --- | --- |
| `evidenceId` (required) | `string` | 1–200 characters; pattern ^[a-zA-Z0-9._:-]+$ | The evidence ID returned by an earlier comparison or analysis result. |

## What it returns

The saved result as it was stored (a period comparison, page comparison or search opportunities result), with the source data versions it used and its input fingerprint. currency is "current" when that data is unchanged, or "historical" when it has since been revised. For period comparisons it also includes sample rows: up to 5 days per window, each with that day's site totals and up to 10 of its queries.

## Notes

- Your access is checked again on every read; sharing an evidence ID doesn't grant access to the site.
- Read-only: it reads data QueryHippo has already stored. It does not start a collection, fetch anything or call an AI model.

## Description your AI sees

> Retrieve an authorized immutable result, source revisions and evidence rows; reports if source revisions have since changed.

## Full schemas

**Input schema**

```
{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "evidenceId": {
      "type": "string",
      "minLength": 1,
      "maxLength": 200,
      "pattern": "^[a-zA-Z0-9._:-]+$"
    }
  },
  "required": [
    "evidenceId"
  ],
  "additionalProperties": false
}
```