> ## Documentation Index
> Fetch the complete documentation index at: https://docs.prometheusprotocol.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Payments

> Understand the user-controlled token allowance system for using paid tools.

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.

<Steps>
  <Step title="See the Allocation Prompt">
    After the standard login and consent, the user will be prompted to set an
    allowance for the service.
  </Step>

  <Step title="Select a Token">
    A dropdown will show the token(s) the service accepts.
  </Step>

  <Step title="Set an Allowance">
    The user enters an amount, setting the maximum total that the service can
    draw from their wallet for future tool calls.
  </Step>
</Steps>

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**.

<Info>
  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.
</Info>