Exchange protocol

Overview

The Exchange protocol is a protocol designed as part of the Fetch.ai uAgents Framework. It defines a standardized method for communication between agents within the agents ecosystem.

The Exchange protocol enables agents to exchange messages using a JSON-based format, which are structured as key-value pairs following the JSON standard. Messages can contain various types of information and are used to convey data and instructions between agents.

Within the protocol, envelopes facilitate communication by encapsulating messages. Envelopes serve as containers for the messages and include additional metadata.

In this protocol, agents can send messages enclosed in envelopes, which are then encoded and sent via HTTP to the endpoints of other agents.

By adhering to the agents Exchange Protocol, agents within the Fetch.ai uAgents ecosystem can communicate with each other using a standardized and interoperable method.

We break down each of these concepts in more detail below.

Core concepts

Messages

Messages consist of key-value pairs following the standard JSON format.

Here are a few examples:

{ "message": "hello" }

{ "name": "alice", "age": 26, "languages": ["English", "Japanese", "Arabic"] }

{ "item": "pretzel", "bid": { "amount": 120, "denomination": "GBP" } }

Once messages are created, these are enclosed in envelopes containing some important metadata.

Envelopes

Envelopes have the following form and are quite similar to blockchain transactions:

@dataclass
class Envelope(BaseModel):
    version: int                     # Envelope version
    sender: str:                     # Bech32-encoded public address of the sender
    target: str:                     # Bech32-encoded public address of the target recipient
    session: UUID4                   # UUID of the session
    schema_digest: str               # Digest of the schema used for the payload
    protocol_digest: Optional[str]   # Optional protocol digest for custom protocols
    payload: Optional[str]           # JSON payload encoded as a base64 string
    expires: Optional[int]           # Unix timestamp in seconds indicating expiration
    nonce: Optional[int]             # Optional nonce
    signature: Optional[str]         # Bech32-encoded signature

Semantics

• The sender field exposes the address of the sender of the message.
• The target field exposes the address of the recipient of the message.
• The protocol contains the unique schema digest string for the message.
• The payload field exposes the payload of the protocol. Its JSON representation should be a base64 encoded string.
• The expires field contains the Unix timestamp in seconds at which the message is no longer valid.
• The signature field contains the signature that is used to authenticate that the message has been sent from the sender agent.

Envelopes are then JSON encoded and sent to endpoints of other agents or services.

Endpoints

The protocol supports only one standardized endpoint: HTTP 1.1 POST /submit, and expects data which is broadly JSON compatible.