Image Generation Request - Mynth - Documentation

Endpoint:

POST https://api.mynth.io/image/generate

Request body

{
  "prompt": "Modern poster design for a jazz festival",
  "negative_prompt": "watermark, blurry text",
  "magic_prompt": true,
  "model": "google/gemini-3.1-flash-image",
  "size": {
    "type": "aspect_ratio",
    "aspectRatio": "4:5",
    "scale": "4k"
  },
  "count": 2,
  "inputs": [
    {
      "type": "image",
      "source": {
        "type": "url",
        "url": "https://example.com/reference.png"
      }
    }
  ],
  "output": {
    "format": "webp",
    "quality": 80
  },
  "webhook": {
    "dashboard": false,
    "custom": [
      {
        "url": "https://example.com/api/mynth-webhook?token=abc123"
      }
    ]
  },
  "rating": {
    "mode": "nsfw_sfw"
  },
  "metadata": {
    "requestId": "req_123"
  },
  "access": {
    "pat": {
      "enabled": true
    }
  }
}

Fields

Field	Type	Default	Notes
`prompt`	`string`	required	Positive prompt, 1–8192 characters.
`negative_prompt`	`string`	—	Optional negative prompt, 1–8192 characters.
`magic_prompt`	`true`	—	Set to `true` to enable Mynth-side prompt enhancement.
`model`	`string`	`"auto"`	A model ID or `"auto"`. Set a specific model in production.
`size`	`string` or object	`"auto"`	Presets, structured aspect ratios, or `"auto"`.
`count`	`number`	`1`	Minimum `1`, maximum `20`.
`inputs`	`array`	`[]`	String URLs or structured image input objects. Maximum 20.
`output`	`object`	`{ "format": "webp", "quality": 80 }`	`format` (`png`, `jpg`, `webp`) and `quality` (`1`–`100`).
`webhook`	`object`	—	`dashboard` (`false`) and `custom` (array of `{ url }`).
`rating`	`true` or object	—	`true`, `{ "mode": "nsfw_sfw" }`, or `{ "mode": "custom", "levels": [...] }`.
`destination`	`string`	—	Name of a configured destination to deliver generated images to.
`metadata`	`object`	—	Arbitrary JSON, maximum 2 KB. Returned with the task and webhook payloads.
`access`	`object`	—	`pat.enabled` (boolean, default `true`). Controls whether a task-scoped access token is returned.

Object details

inputs entry:

{
  "type": "image",
  "source": {
    "type": "url",
    "url": "https://example.com/reference.png"
  }
}

String URLs are a shorthand for image inputs. Structured entries use type and source. webhook object:

{
  "dashboard": false,
  "custom": [{ "url": "https://example.com/hook" }]
}

Set dashboard: false to skip dashboard-managed webhooks for this task. Maximum 5 custom endpoints. Custom endpoints are not signed. See Use Webhooks. access object:

{
  "pat": { "enabled": true }
}

Returns a publicAccessToken for browser-safe polling. See Browser Polling.

Prompt enhancement

Set magic_prompt: true to opt into Mynth-side prompt enhancement. When enabled, the enhanced prompt is returned in result.magic_prompt (with positive and optional negative).

Size presets

square
portrait
landscape
portrait_tall
landscape_wide
1:1
2:3
3:2
3:4
4:3
4:5
5:4
9:16
16:9
21:9
2:1
1:2
1:1_4k
2:3_4k
3:2_4k
3:4_4k
4:3_4k
4:5_4k
5:4_4k
9:16_4k
16:9_4k
21:9_4k
2:1_4k
1:2_4k

Structured size objects

Aspect ratio

{ "type": "aspect_ratio", "aspectRatio": "16:9" }

Supported aspect ratios:

1:1
2:3
3:2
3:4
4:3
4:5
5:4
9:16
16:9
21:9
2:1
1:2

Optional scale values:

base (default)
4k

When scale: "4k" is requested, models with dedicated 4K pricing are billed at their 4K rate. For each successful output image, input images are billed as perImage + perInput * inputs.length.

Auto

{ "type": "auto" }

Mynth picks the size automatically. When the model can size natively, that path is used; otherwise Mynth resolves a size for you. This is not configurable.

​Request body

​Fields

​Object details

​Prompt enhancement

​Size presets

​Structured size objects

​Aspect ratio

​Auto