Function mcp_call_tool_gated 

pub fn mcp_call_tool_gated(
    agent_slug: String,
    tool_name: String,
    arguments_json: String,
    principal_permitted: bool,
) -> Result<String, String>

Principal-gated MCP tool call. principal_permitted = false → Err without MCP. Tool must be on the agent’s allowed_mcp_tools (or *); empty allowlist denies all.