What happened
The request was well-formed but failed schema validation. One or more fields violated type, format, range, or presence constraints. Theerrors array contains one entry per field. Each includes a location (e.g. body.items[3].name) and a message describing the violation.
A malformed page cursor (truncated, padded, re-encoded, or not a cursor at all) fails validation too, located at the cursor parameter it was passed in: query.cursor on most lists, query.matches_cursor for the matches of an alert delivery. It is never read as a request for the first page. A few lists use their own cursor format and report a bad one their own way: company ad placements, the expert directory (GET /v1/people/expertise), and the episode feed return 422 without a parameter location, and invoices pass the cursor to the billing provider.
How to fix
Inspect theerrors array, fix the offending fields, and retry. For a rejected cursor, pass it exactly as the previous response returned it, or omit it to start from the first page.