BAD_REQUEST

The request was malformed and never reached the validation contract. HTTP 400. The message names the field and the shape expected.

The request could not be read as the route expects: a body that is not JSON, a required field missing, a claims value that is a string but not JSON, a hash that is not a hash.

The envelope

{"ok": false,
 "error": {"code": "BAD_REQUEST",
           "message": "claims must be an object mapping each claim name to its value, got list",
           "docs": "https://docs.agents.jaxon.ai/errors/bad-request.md"},
 "versions": {"...": "..."}}

This is distinct from VALIDATION_REJECTED: that code means the request was well-formed and the values did not satisfy the ruleset. This one means the request itself could not be interpreted.

Common causes

**claims sent as a JSON string that is not valid JSON.** A string is accepted (models do this) if it parses to an object; "{amount: 5}" does not.
**Neither ruleset_hash nor source on a check.** One of the two is required.
A hash that is not a content hash. Hashes are lowercase hex; a name goes to dsail_load_ruleset, not to ruleset_hash.
**A body that is not application/json.**
A converter with a non-numeric factor, or an attribution missing on dsail_add_unit_converter.

The fix

Read message; it names the field. The REST API reference shows every request body, and the MCP tools reference every tool's arguments.