Skip to main content
Many services in the App Store are monetized. The Prometheus Protocol handles this through a secure and user-friendly token allowance system. As an agent developer or user, it’s important to understand this flow. The core principle is that the user is always in control. A service can never take funds without explicit permission. This permission is granted by the user in the form of an “allowance”—a specific amount of a token that a specific service is allowed to withdraw over time.

​
The Proactive Approach: Allocation During Login

The easiest way to handle payments is during the initial authentication flow. When a user connects to a paid service for the first time, the OAuth consent screen will include an extra, optional step for payment allocation.
1

See the Allocation Prompt

After the standard login and consent, the user will be prompted to set an allowance for the service.
2

Select a Token

A dropdown will show the token(s) the service accepts.
3

Set an Allowance

The user enters an amount, setting the maximum total that the service can draw from their wallet for future tool calls.
By setting an allowance up-front, all subsequent paid tool calls will work seamlessly until the allowance is depleted.

​
The Reactive Approach: Handling Insufficient Funds

What happens if a user skips the initial allocation, or if their allowance runs out? In this case, a call to a paid tool will fail, but it will fail gracefully. The MCP server will return a text message explaining the situation and providing a direct link to the Prometheus Approvals Dashboard.
This response will include a direct link to the Prometheus Approvals Dashboard, a secure web application where the user can manage their allowances for all services.
⌘I