---
title: "Image description"
method: POST
path: "/v1/describe"
tags: ["Image description"]
---

# Image description

`POST /v1/describe`

## Request

- Base URL: `https://api.thecompound.tech`
- URL: `https://api.thecompound.tech/v1/describe`
- Auth: HTTP bearer

ParseRail evaluates an image and returns accessible alt text, a caption, tags, and any text found inside it. One call supports accessibility and catalogs.

Cost: 3 credits ($0.03) — charged only on success.

## Headers

- `ParseRail-Dry-Run` '1' | 'true'
- `Idempotency-Key` string

## Request body

- object: Provide image or imageUrl.
  - `image` object
    - `data` string, required: Base64.
    - `mimeType` string, required
  - `imageUrl` string, uri
  - `purpose` 'alt' | 'caption' | 'product' | 'detailed'

## Response `200`

The call succeeded. The response contains result fields and a usage envelope. With `ParseRail-Dry-Run: 1` the body is a DryRun object instead.

- union
  - object
    - `altText` string, required: Concise, accessibility-grade.
    - `caption` string, required
    - `detailed` string, nullable: Long-form description when purpose=detailed.
    - `tags` string[], required
    - `embeddedText` string, nullable: Return any text found inside the image.
    - `usage` Usage, required
      - `credits` integer, required: Credits burned by this call.
      - `balanceRemaining` integer, required: Wallet balance after the charge.
  - DryRun: A dry run: auth, the per-key throttle, body validation and the balance precheck ran. No model ran and nothing was charged.
    - `dryRun` true, required
    - `valid` true, required: The body passed validation. An invalid body returns 400 instead.
    - `endpoint` string, required
    - `wouldCharge` integer, required: Credits a successful live call would charge.
    - `balance` integer, required: Your wallet balance now.
    - `liveStatus` 200 | 202 | 402, required: The status a live call with this body would get: 402 when the balance or the key's monthly cap cannot cover it, 202 for `async: true`, else 200.
    - `keyCapRemaining` integer: Present when the key carries a monthly cap: credits left under it this month.
    - `usage` Usage, required
      - `credits` integer, required: Credits burned by this call.
      - `balanceRemaining` integer, required: Wallet balance after the charge.
    - `requestId` string, required

## Other responses

- `400`: Invalid request body.
- `401`: Missing or invalid API key.
- `402`: `insufficient_credits`: the balance cannot cover the call. `spend_cap_reached`: the key has reached its monthly cap. Nothing is charged.
- `429`: Rate limit exceeded.

---

[API](https://skmtc.dev/thecompound/apis/parserail.md) · [All operations](https://skmtc.dev/thecompound/apis/parserail/llms.txt) · [OpenAPI document](https://skmtc.dev/thecompound/apis/parserail/revisions/7895a3b7812b?raw)