## TL;DR

The image lacks the detail needed to verify a signature, and no algorithm can invent it. Request a higher-resolution capture of the receipt, and until one arrives, route the expense to manual review rather than auto-failing it.

## Error

```text
agent failed to verify the receipt signature: image too low-res
```

## Steps

1. Check the image resolution and the signature region's pixel size. Expected: you confirm the signature area is too small to analyze.
2. Request a re-capture at higher resolution, with the signature area filling a good portion of the frame. Expected: a submittable higher-res image.
3. While waiting, route the expense to manual review with a note that signature verification is pending. Expected: the expense is not auto-rejected for a capture problem.
4. When the new image arrives, re-run verification. Expected: a definitive pass or fail on adequate pixels.
5. Set a minimum capture resolution in the submission guidance. Expected: fewer low-res submissions over time.

## When to use

- Signature verification fails specifically on low resolution.
- The signature exists but cannot be analyzed.

## When not to use

- There is no signature at all (request the signature, not a better photo).
- Verification fails on a high-res image (a matcher problem, different fix).

## Tool compatibility

- Custom agent verification pipelines; mobile capture guidance.

## Variant phrasings

### Signature unverifiable: resolution too low

Same failure, alternate wording.

### Image quality insufficient for signature check

The quality-gate phrasing.

## Why it happens

Signature verification needs fine stroke detail. Downscaled or distant photos destroy that detail, and the verifier correctly refuses to judge what it cannot see.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_nCruHNVlL2raAnhZW1VndQ