diff --git a/src/lib.rs b/src/lib.rs
index f46edac..be1ac41 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -60,7 +60,7 @@ pub use self::params::*;
 pub use self::patch::*;
 pub use self::eval::{State, Machine, Runtime, MachineStatus};
 pub use self::commit::{AccountCommitment, AccountChange, AccountState, BlockhashState, Storage};
-pub use self::transaction::{ValidTransaction, TransactionVM};
+pub use self::transaction::{ValidTransaction, TransactionVM, UntrustedTransaction};
 pub use self::errors::{OnChainError, NotSupportedError, RequireError, CommitError, PreExecutionError};
 pub use self::util::opcode::Opcode;
 pub use block_core::TransactionAction;
diff --git a/src/transaction.rs b/src/transaction.rs
index cbe72c8..23d99eb 100644
--- a/src/transaction.rs
+++ b/src/transaction.rs
@@ -41,11 +41,17 @@ macro_rules! system_address {
 #[derive(Debug, Clone)]
 /// Represents an untrusted Ethereum transaction.
 pub struct UntrustedTransaction {
+    /// The caller. Must be attached with its commitment,
     pub caller: AccountCommitment,
+    /// Transaction gas price.
     pub gas_price: Gas,
+    /// Transaction gas limit.
     pub gas_limit: Gas,
+    /// Action CALL/CREATE of the transaction.
     pub action: TransactionAction,
+    /// Value sent with this transaction.
     pub value: U256,
+    /// Transaction input.
     pub input: Rc<Vec<u8>>,
 }