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Practical limits

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Image generation

  • count maximum: 20
  • prompt length maximum: 8192 characters
  • negative prompt length maximum: 8192 characters
  • inputs maximum per request: 20
  • input shortcut maximum length: 2048 characters
  • custom webhook endpoints per request: 5
  • destination name maximum length: 64 characters
  • metadata maximum size: 2 KB

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Content rating

  • URLs per request maximum: 10
  • custom levels minimum: 2
  • custom levels maximum: 7
  • custom level value max length: 24
  • custom level description max length: 150

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Alt text

  • URLs per request maximum: 10
  • alt text maximum length: 160 characters

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Uploads

  • maximum files per request: 10
  • maximum file size: 10 MB
  • minimum file size: 1 KB
  • maximum request body size: 100 MB
  • accepted formats: JPEG, PNG, WEBP

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Concurrency

Mynth does not enforce API concurrency limits. If you want to create many independent tasks, you can send requests in parallel.

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Error response shape

Every API error returns a JSON body with a machine-readable code and a human-readable message: 
{
  "code": "VALIDATION_ERROR",
  "message": "Count cannot exceed 20 images per request"
}
Codes are stable and SCREAMING_SNAKE_CASE. message is informational and may change; do not parse it.

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Common failure cases

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Unauthorized

HTTP 401 with code: "UNAUTHORIZED". You used:
  • a missing or invalid API key
  • a Public Access Token on an owner-only endpoint
  • a task token for the wrong task
{
  "code": "UNAUTHORIZED",
  "message": "Invalid API key"
}

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Validation errors

HTTP 400 with code: "VALIDATION_ERROR". The request shape does not match what Mynth expects, or the selected model does not support a requested capability such as input images. 
{
  "code": "VALIDATION_ERROR",
  "message": "The selected model does not support input images."
}

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Insufficient balance

HTTP 422 with code: "INSUFFICIENT_BALANCE". Task creation reserves cost before generation begins. Requests fail when the account does not have enough available balance. 
{
  "code": "INSUFFICIENT_BALANCE",
  "message": "Insufficient balance."
}

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Spending limit exceeded

HTTP 429 with code: "SPENDING_LIMIT_EXCEEDED". The reserved cost would push the API key’s spending limit past its configured cap for the current period. See Authentication. 
{
  "code": "SPENDING_LIMIT_EXCEEDED",
  "message": "Spending limit exceeded"
}

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Upload too large

HTTP 413 with code: "VALIDATION_ERROR". The upload request body exceeds the maximum size. 
{
  "code": "VALIDATION_ERROR",
  "message": "Upload body is too large"
}

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Not found

HTTP 404 with code: "TASK_NOT_FOUND". The task ID does not exist, or you do not have access to it. 
{
  "code": "TASK_NOT_FOUND"
}

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Task failed

The task was accepted but did not complete successfully. This is not an HTTP error. Polling will eventually return status: "failed", and webhook delivery will emit task.image.generate.failed.

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SDK-specific errors

The JavaScript SDK can also throw:
  • MynthAPIError - wraps all API errors with the HTTP status and the error code
  • TaskAsyncTimeoutError - wait() polled for five minutes without completion
  • TaskAsyncUnauthorizedError - the Public Access Token was rejected
  • TaskAsyncFetchError - a network fetch failed during polling
  • TaskAsyncTaskFetchError - the task detail fetch failed
  • TaskAsyncTaskFailedError - the task completed with status: "failed"
Catch MynthAPIError to inspect the underlying API error: 
import { MynthAPIError } from "@mynthio/sdk";

try {
  const task = await mynth.image.generate({ prompt: "..." });
} catch (error) {
  if (error instanceof MynthAPIError) {
    console.error(error.status); // HTTP status code
    console.error(error.code); // API error code, e.g. "VALIDATION_ERROR"
  }
}