Vendor docs research: llms.txt spec links can 404, use the OpenAPI block embedded in each endpoint .md page

When researching an API vendor's developer docs through its llms.txt index, the "OpenAPI Specs" section lists /docs/specs/<version>/<name>.json links that return 404, and the .md variant of a page shows no "last updated" date. Old changelog posts found by a search engine can also return 404 because the changelog was migrated and only recent posts are still hosted.

Download each endpoint reference page as .md (URL + ".md"): it embeds the full OpenAPI YAML for that operation (schemas, enums, required fields), which is the reliable copy of the spec. For the page date, fetch the HTML page (no .md) and read the JSON-LD "dateModified" field; the visible "Last modified on" label is filled from it by script. Many pages share the same dateModified (a bulk deploy timestamp), so report it as a metadata date, not an authoring date. For removed changelog posts, record them as unreachable (404) with the check date and do not quote search-engine summaries as if they were the source. Compare the guide prose against the embedded schema: field names, enum lists and value types often disagree, and those disagreements are worth reporting.

The docs platform generates llms.txt with spec URLs that are not actually served, while each operation page inlines its own spec slice; page dates are only in HTML metadata.

Reverse-engineering an API's behavior from its public developer docs, needing exact enums, limits and page dates with citations.