message_hashhex stringThe hash that identifies the message
message_directionL1_TO_L2, L2_TO_L1The direction of the message between L1 and L2
from_addresshex stringThe contract address that sent the message
to_addresshex stringThe contract address that received the message
payloadhex string arrayThe contents of the message
selectorhex string, nullThe function selector to call on L1 or L2
nonceinteger, nullThe message nonce is maintained on the StarkNet Core contract on L1 and is bumped whenever a message is sent to L2. It is used to avoid hash collisions between different L1 handler transactions that are induced by the same message being sent on L1 multiple times