invalid_frontmatter

HTTP status: 422 Unprocessable Content · Charged: no

What it means

The block between the two --- lines at the top of the document is not valid YAML. The response tells you where the parser stopped: line and column count from the first line of the document, and message is the parser’s own description. kind is invalid_yaml.

What to do

Go to the line and column in the response and check the usual causes:

1. Indentation. Use spaces, never tabs, and keep keys at the same level aligned.
2. Colons inside values. A value such as title: Release: October needs quotes: title: "Release: October".
3. A missing colon after a key.

Fix the document and call again.

Example response

Captured from the production API on 2026-10-13. The document had date: 2026-10-13 indented under title, which YAML reads as a broken mapping.

{
  "error": "invalid_frontmatter",
  "hint": "The frontmatter block between `---` delimiters is not valid YAML. Check indentation (2 spaces, no tabs), quoting on values with special characters, and colons after every key. The `line` and `column` fields point to the first parser failure.",
  "kind": "invalid_yaml",
  "message": "bad indentation of a mapping entry",
  "line": 3,
  "column": 7,
  "docs_url": "https://docs.markdownscribe.com/errors/invalid_frontmatter",
  "request_id": "01M4TRDFZ9G5EFRNK42RN2XQJH"
}

Related

• validation: the request body itself is the wrong shape.