> ## Documentation Index
> Fetch the complete documentation index at: https://www.agentcommercekit.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Components and Roles
> Key components and their roles within the ACK-Pay payment protocol.
## Role Definitions
The ACK-Pay protocol defines several key components that interact to facilitate payments:
* **Client Applications and Client Agents:** Software initiating service requests or payments on behalf of end-users or autonomous processes. In the Client-Initiated sequence, they are responsible for constructing the Payment Request.
* **Servers, Server Agents and Service Providers:** Entities providing resources or services that may require payment and need to verify payment receipts before granting access or fulfilling requests. In the Server-Initiated sequence, they are responsible for generating and sending the Payment Request.
* **Payment Service:** A crucial intermediary responsible for managing payment execution. Its functions can include:
* Routing payments across different networks.
* Assisting Clients in constructing Payment Requests (in Client-Initiated sequences).
* Handling currency/asset conversions.
* Interacting with underlying Settlement Networks.
* Performing risk assessments and compliance verification (potentially using ACK-ID).
* Managing human approval workflows.
* Coordinating with Receipt Services.
* Abstracting diverse payment methods, including traditional rails (ACH, card networks via APIs like Visa Intelligent Commerce or Mastercard Agent Pay), and blockchain networks.
* Optionally acting as a bridge to other protocols by exposing compatible interfaces (e.g., functioning as an x402 Facilitator for servers using that approach).
* **Receipt Service:** Generates and validates cryptographically verifiable receipts (typically as Verifiable Credentials), ensuring:
* Secure credential issuance based on confirmed payment settlement.
* Management of receipt status (e.g., validity, revocation).
* Validation of presented receipts. *(Note: The Payment Service and Receipt Service roles may sometimes be fulfilled by the same entity).*
* **Settlement Networks:** The underlying financial infrastructures that execute value transfer (e.g., traditional banking systems, card networks, blockchain networks).
These roles define the actors within the ACK-Pay ecosystem that orchestrate payment flows. The next section will explore how these actors collaborate with one another.
## Component Interactions with a Payment Service
The following component activity diagram illustrates a sophisticated flow involving a Payment Service.
## Component Interactions with Client-Executed Payments
The following component activity diagram illustrates a simple flow in which a Client Agent executes a payment directly via an embedded Payment Service.
