Here are the data structures with brief descriptions:

otActiveScanResult
otBorderRouterConfig
otBufferInfo
otChildInfo
otCoapHeader
otCoapOption
otCoapResource
otCommissioningDataset
otDhcpAddress
otDnsQuery
otEidCacheEntry
otEnergyScanResult
otExtAddress
otExtendedPanId
otExternalRouteConfig
otIcmp6Handler
otIcmp6Header
otIp6Address
otIp6Prefix
otLeaderData
otLinkModeConfig
otMacBlacklistEntry
otMacCounters
otMacWhitelistEntry
otMasterKey
otMeshLocalPrefix
otMessage
otMessageInfo
otMessageQueue
otNcpLegacyHandlers
otNeighborInfo
otNetifAddress
otNetifMulticastAddress
otNetworkName
otOperationalDataset
otPlatUsecAlarmTime
otPSKc
otRouterInfo
otSecurityPolicy
otSemanticallyOpaqueIidGeneratorData
otSockAddr
otSteeringData
otUdpSocket
RadioPacket