calesthio/OpenMontage · error · ValueError

prompt is required

Error message

prompt is required

What it means

Raised by KlingOfficialImage._prompt when the 'prompt' input is missing, empty, or whitespace-only after stripping. The Kling image API requires a non-empty text prompt, so the tool refuses before making any network call. This is a pure input-validation error and costs nothing when raised.

Source

Thrown at tools/graphics/kling_official_image.py:396

            client.download(url, output_path)
            paths.append(output_path)
        return paths

    @staticmethod
    def _output_url(item: dict[str, Any]) -> str:
        url = item.get("url") or item.get("image_url") or item.get("resource_url")
        if url:
            return str(url)
        resource = item.get("resource") or {}
        if isinstance(resource, dict) and resource.get("url"):
            return str(resource["url"])
        raise ValueError(f"Kling image response item contained no downloadable URL: {item}")

    @staticmethod
    def _prompt(inputs: dict[str, Any]) -> str:
        prompt = str(inputs.get("prompt") or "").strip()
        if not prompt:
            raise ValueError("prompt is required")
        return prompt

    @staticmethod
    def _copy_common_task_fields(inputs: dict[str, Any], payload: dict[str, Any]) -> None:
        if "watermark" in inputs:
            payload["watermark_info"] = {"enabled": bool(inputs.get("watermark"))}
        callback_url = validate_callback_url(inputs.get("callback_url"))
        if callback_url:
            payload["callback_url"] = callback_url
        if inputs.get("external_task_id"):
            payload["external_task_id"] = inputs["external_task_id"]

    @staticmethod
    def _reference_metadata_from_generation_payload(payload: dict[str, Any]) -> list[dict[str, Any]]:
        references: list[dict[str, Any]] = []
        if payload.get("image"):
            references.append({"kind": "image", "source_type": "image"})
        if payload.get("element_list"):

View on GitHub (pinned to 95e1c3d0ab)

Solutions

1. Supply a non-empty prompt string (strip check applies)
2. If the prompt is composed dynamically, fall back to a default descriptor when composition yields empty text
3. Validate inputs before invoking the tool in pipeline code

Example fix

# before
inputs = {"image": "ref.png"}
# after
inputs = {"image": "ref.png", "prompt": "cinematic portrait, soft rim light"}

prompt = str(inputs.get("prompt") or "").strip()
if not prompt:
    raise ValueError("prompt required before kling_official_image")
inputs["prompt"] = prompt

When it happens

Trigger: Calling kling_official_image with prompt omitted, set to '' or ' ', or built from a template variable that resolved to an empty string (e.g. caption/topic pipeline produced no text).

Common situations: Agent pipelines composing prompts from optional upstream fields (subject/scene/style) where all parts were empty; passing only an image reference expecting img2img without prompt because a sibling tool allowed it.

Related errors

• MiniMax image generation requires 'prompt'.
• prompt is required
• prompt references <<<image_{max(existing_numbers)}>>> but on
• Image Omni prompt placeholders must start at <<<image_1>>>
• Kling avatar requires image_url or image_path

AI-assisted analysis of calesthio/OpenMontage@95e1c3d0ab (2026-08-15). Data as JSON: /api/errors/456f7194d9f7c256. Report an issue: GitHub.