Error Codes - Steerholm

Steerholm returns structured JSON-RPC errors with codes outside the reserved JSON-RPC range.

Error codes

Code	Name	Meaning
`-31001`	`AUTHORIZATION_DENIED`	The operation violates the user’s security policy
`-31002`	`SERVER_UNAVAILABLE`	The target MCP server is not reachable

Response format

Errors include an error_type field in the data payload:

{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -31001,
    "message": "Tool 'git_commit' on server 'git' is not allowed.",
    "data": {
      "error_type": "AUTHORIZATION_DENIED"
    }
  }
}

Behavior

AUTHORIZATION_DENIED

Returned when:

The agent calls a tool not in its policy
The agent calls a tool with arguments that violate an argument policy
The agent calls a tool that doesn’t exist on any server it has access to

The agent must not retry the same operation — the denial is authoritative.

SERVER_UNAVAILABLE

Returned when the target MCP server process is not running or not reachable. The agent may retry — the server might become available later.