diff --git a/src/Simplex/Messaging/Agent/Command.hs b/src/Simplex/Messaging/Agent/Command.hs
new file mode 100644
index 000000000..411d5c96d
--- /dev/null
+++ b/src/Simplex/Messaging/Agent/Command.hs
@@ -0,0 +1,87 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# OPTIONS_GHC -fno-warn-unticked-promoted-constructors #-}
+
+module Simplex.Messaging.Agent.Command where
+
+import Data.ByteString.Char8 (ByteString)
+import Data.Kind
+import Data.Time.Clock
+import Network.Socket
+import Simplex.Messaging.Server.Transmission (Encoded, MsgBody, PublicKey, QueueId)
+
+data AParty = Agent | User
+  deriving (Show)
+
+data SAParty :: AParty -> Type where
+  SAgent :: SAParty Agent
+  SUser :: SAParty User
+
+deriving instance Show (SAParty a)
+
+data ACommand (a :: AParty) where
+  NEW :: SMPServer -> Maybe ConnectionName -> AckMode -> ACommand User
+  INV :: ConnAlias -> SMPQueueInfo -> ACommand Agent
+  JOIN :: SMPQueueInfo -> Maybe SMPServer -> Maybe ConnectionName -> AckMode -> ACommand User
+  CON :: ConnAlias -> ACommand Agent
+  CONF :: ConnAlias -> OtherPartyId -> ACommand Agent
+  LET :: ConnAlias -> OtherPartyId -> ACommand User
+  SUB :: ConnAlias -> SubMode -> ACommand User
+  END :: ConnAlias -> ACommand Agent
+  QST :: ConnAlias -> QueueDirection -> ACommand User
+  STAT :: ConnAlias -> QueueDirection -> Maybe ConnState -> Maybe SubMode -> ACommand Agent
+  SEND :: ConnAlias -> MsgBody -> ACommand User
+  MSG :: ConnAlias -> AgentMsgId -> UTCTime -> UTCTime -> MsgStatus -> MsgBody -> ACommand Agent
+  ACK :: ConnAlias -> AgentMsgId -> ACommand User
+  RCVD :: ConnAlias -> AgentMsgId -> ACommand Agent
+  OFF :: ConnAlias -> ACommand User
+  DEL :: ConnAlias -> ACommand User
+  OK :: ConnAlias -> ACommand Agent
+  ERR :: ConnAlias -> ErrorType -> ACommand Agent
+
+data AMessage where
+  HELLO :: VerificationKey -> AckMode -> AMessage
+  REPLY :: SMPQueueInfo -> AMessage
+  A_DEL :: AMessage
+  A_MSG :: AgentMsgId -> UTCTime -> MsgBody -> AMessage
+  A_ACK :: AgentMsgId -> AckStatus -> AMessage
+
+data SMPServer = SMPServer HostName ServiceName KeyFingerprint
+
+type KeyFingerprint = Encoded
+
+type ConnAlias = ByteString
+
+type ConnectionName = ByteString
+
+type OtherPartyId = Encoded
+
+data Mode = On | Off
+
+newtype AckMode = AckMode Mode
+
+newtype SubMode = SubMode Mode
+
+data SMPQueueInfo = SMPQueueInfo SMPServer QueueId EncryptionKey
+
+type EncryptionKey = PublicKey
+
+type VerificationKey = PublicKey
+
+data QueueDirection = SND | RCV
+
+data ConnState = New | Pending | Confirmed | Secured | Active | Disabled
+
+type AgentMsgId = Int
+
+data MsgStatus = MsgOk | MsgError MsgErrorType
+
+data MsgErrorType = MsgSkipped AgentMsgId AgentMsgId | MsgBadId AgentMsgId | MsgBadHash
+
+data ErrorType = UNKNOWN | PROHIBITED -- etc.
+
+data AckStatus = AckOk | AckError AckErrorType
+
+data AckErrorType = AckUnknown | AckProhibited | AckSyntax Int -- etc.