Constant IDENTITY_VALIDATE_TOOL 

pub(crate) const IDENTITY_VALIDATE_TOOL: &str = r#"{
  "name": "IdentityValidate",
  "description": "Live-probe one of your own linked accounts against its provider using the stored key, to confirm the credential still works. You never supply a secret — pass an account_id from IdentityAccounts. Returns valid, status, masked_tail, and error.",
  "inputSchema": {
    "type": "object",
    "properties": {
      "account_id": { "type": "string", "description": "One of your linked accounts (from IdentityAccounts)" }
    },
    "required": ["account_id"]
  }
}"#;