McpError
Error body of POST /v1/mcp when the request never reaches JSON-RPC — authentication,
rate limiting, wrong method, or an unreachable upstream. Deliberately not the
standard envelope: MCP clients do not understand it.
errorstring
invalid_token, too_many_requests, Only POST is supported on this endpoint, or
MCP upstream is unavailable.
Example:
invalid_tokenMcpError
{
"error": "invalid_token"
}