mcp_argument_type

An argument is the wrong type. Answered with 400.

What it means

An argument arrived as a different JSON type than the tool's inputSchema declares. A null is a value here rather than an absence: only a parameter the schema advertises as nullable accepts one.

What to do

Send the argument as the type the detail names and call the tool again.

The body

{
  "type": "https://tigby.eu/problems/mcp_argument_type",
  "title": "An argument is the wrong type",
  "status": 400,
  "detail": "…what was refused, naming this request's own values",
  "code": "mcp_argument_type",
  "doc_url": "https://docs.tigby.eu/errors/mcp_argument_type",
  "agent_hint": "…the next step, for software"
}

Branch on code. The detail names this request's own Handle, id or limit and is not part of the contract.