| Class name | Class description |
| BeaconId | Beacon ID, which can either be an iBeacon ID or an Eddystone UID. The ID is broadcast by BLE beacons. |
| Message | Message that will be shared with nearby devices. The message contains client-specified content and a type. |
| MessagePicker | Specifies the set of message to be received. When the sharing code is discovered, the MessagePicker must match the message. A MessagePicker is the logical OR of multiple pickers. |
| MessageHandler | Callback for events such as signal change, distance change, message detection, and finding that a message is not longer detectable. |
| MessageOption | Represents options for calling the Message API. |
| Permission | Nearby permission. Calling the Message#Put or Message#Get API requires a corresponding permission. |
| StatusCallback | Callback for MessageEngine status changes. |
| Policy | Describes a set of policies for publishing or subscribing to messages. |
| PutOption | Options for calling #Put. |
| PutCallback | Callback for events related to message publishing. |
| GetOption | Options for calling #Get. |
| GetCallback | Callback for events related to message subscription. |
| MessageEngine | Defines a set of APIs to publish or subscribe to messages between nearby devices. |