danny-avila/LibreChat · error · Error

Missing required field: prompt

Error message

Missing required field: prompt

What it means

Runtime guard at the top of the image_gen_oai tool callback: the destructured `prompt` must be present before it constructs the OpenAI client and calls images.generate. Thrown before any network I/O.

Source

Thrown at api/app/clients/tools/structured/OpenAIImageTools.js:127

  const imageFiles = fields.imageFiles ?? [];

  /**
   * Image Generation Tool
   */
  const imageGenTool = tool(
    async (
      {
        prompt,
        background = 'auto',
        n = 1,
        output_compression = 100,
        quality = 'auto',
        size = 'auto',
      },
      runnableConfig,
    ) => {
      if (!prompt) {
        throw new Error('Missing required field: prompt');
      }
      const clientConfig = { ...closureConfig };
      const proxyDispatcher = getProxyDispatcher();
      if (proxyDispatcher) {
        clientConfig.fetchOptions = {
          dispatcher: proxyDispatcher,
        };
      }

      /** @type {OpenAI} */
      const openai = new OpenAI(clientConfig);
      let output_format = imageOutputType;
      if (
        background === 'transparent' &&
        output_format !== EImageOutputType.PNG &&
        output_format !== EImageOutputType.WEBP
      ) {
        logger.warn(

View on GitHub (pinned to 5ff282f900)

Solutions

1. Always include a non-empty `prompt` string in the tool-call arguments.
2. Mark `prompt` as required in the tool schema.
3. Validate args at the boundary before invoking the tool.
4. Inspect the raw tool-call JSON to confirm the model is emitting `prompt` and not a synonym.

Example fix

// before
await imageGenTool.invoke({ size: '1024x1024' }); // throws

// after
await imageGenTool.invoke({ prompt: 'a fox in snow', size: '1024x1024' });

function buildImageGenArgs(input) {
  if (typeof input.prompt !== 'string' || !input.prompt.trim()) {
    throw new Error('image_gen_oai requires a non-empty prompt.');
  }
  return input;
}

function hasPrompt(arg) {
  return typeof arg?.prompt === 'string' && arg.prompt.trim().length > 0;
}

try {
  await imageGenTool.invoke(args);
} catch (e) {
  if (/Missing required field: prompt/.test(e.message)) return 'A prompt is required to generate an image.';
  throw e;
}

When it happens

Trigger: The OpenAI image-generation tool is invoked with a payload where `prompt` is missing/null/empty — e.g., only quality/size/background were supplied.

Common situations: The model emitted tool args without prompt; the JSON schema does not mark prompt required so the model omitted it; programmatic caller built args from optional input; refactoring renamed the field.

Related errors

• Missing required field: prompt
• Missing required field: prompt
• Missing required field: prompt
• Missing required field: finetune_id for finetuned generation
• Invalid endpoint for finetuned generation. Must be one of: $

AI-assisted analysis of danny-avila/LibreChat@5ff282f900 (2026-08-12). Data as JSON: /api/errors/1578711e0aca2edc. Report an issue: GitHub.