validation

HTTP status: 400 Bad Request · Charged: no

What it means

The body of the request could not be used. Either it is not valid JSON, or a field is missing, has the wrong type, or is not allowed. The details array lists every field that failed, with its path, a code and a message. When the body is not JSON at all, details holds a single entry with code invalid_json.

What to do

1. Send Content-Type: application/json and a well-formed JSON object.
2. Read details: each entry names the field (path) and why it failed (message).
3. Check the expected body for the endpoint. The four Markdown operations take { "markdown": "<string>" }; Mermaid takes exactly one of { "diagram": "..." } or { "markdown": "..." }. The full contract is the OpenAPI document.

Example response

Captured from the production API on 2026-10-13, calling POST /v1/md/lint with { "text": "# Hi" } instead of markdown.

{
  "error": "validation",
  "hint": "The request body did not match the expected shape. See `details` for each field that failed. The endpoint expects `{ \"markdown\": \"<string>\" }`.",
  "details": [
    {
      "path": ["markdown"],
      "code": "invalid_type",
      "message": "Invalid input: expected string, received undefined"
    }
  ],
  "docs_url": "https://docs.markdownscribe.com/errors/validation",
  "request_id": "01M4TRDFQJR0KEGWCTQ7EAEB4P"
}

Related

• invalid_request: the same kind of problem on URL to Markdown.
• payload_too_large: the body is valid but too big.