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

# Core Concepts

> Understand the fundamental building blocks of Nevermined: AI Agents and Payment Plans.

At the heart of Nevermined are two fundamental concepts: **AI Agents** and **Payment Plans**. Understanding how they work together is key to monetizing your AI services.

## What is an AI Agent?

In the Nevermined ecosystem, an AI Agent is any digital service or tool that you want to monetize. It's more than just a model; it's a complete service that can:

* **Make and receive digital payments** in both crypto and fiat.
* **Expose its functionalities** through HTTP API endpoints.
* **Be discovered and accessed** by subscribers through flexible payment plans.
* **Validate access** using bearer token authentication.
* **Track usage** with automatic credit redemption.

Nevermined provides the tools to wrap your existing AI service—whether it's a single model, a complex workflow, or a multi-agent system—and turn it into a monetizable product without needing to build a billing system from scratch.

### Agent Components

<CardGroup cols={2}>
  <Card title="Metadata" icon="tags">
    Name, description, tags, and creation date for discovery.
  </Card>

  <Card title="API Endpoints" icon="plug">
    HTTP endpoints that define how to interact with your agent.
  </Card>

  <Card title="Payment Plans" icon="money-bill">
    One or more plans that define pricing and access terms.
  </Card>

  <Card title="Access Control" icon="shield">
    Token-based authentication through Nevermined Proxy or direct validation.
  </Card>
</CardGroup>

## What is a Payment Plan?

A Payment Plan is a set of rules and conditions that define how subscribers pay to access your AI Agent. Plans are highly flexible and are defined by two main components: their **price** and the **consumption** model.

### Key Attributes of a Payment Plan:

<CardGroup cols={2}>
  <Card title="Payment Type" icon="credit-card">
    Choose whether to charge in **Crypto** (any ERC-20 token or native coin) or **Fiat** (via Stripe integration).
  </Card>

  <Card title="Price Configuration" icon="sack-dollar">
    Set the total price for the plan and define how the revenue is distributed among one or more receivers. Supports multi-receiver splits.
  </Card>

  <Card title="Plan Types" icon="calendar-days">
    * **Time-based**: Limited by duration (e.g., 30 days, 1 year)
    * **Credits-based**: Limited by usage (e.g., 100 queries)
    * **Trial**: Free limited access for testing
  </Card>

  <Card title="Credit System" icon="coins">
    Define how many credits a subscriber receives upon purchase and how many are consumed per request. Supports:

    * Fixed credits per request
    * Dynamic consumption based on query complexity
    * Minimum/maximum thresholds for redemption
  </Card>
</CardGroup>

### Plan Configuration Types

<AccordionGroup>
  <Accordion title="Credits-Based Plans">
    Perfect for usage-based pricing models:

    * **Fixed Credits**: Set amount of credits (e.g., 100 credits)
    * **Credits per Request**: How many credits each query consumes
    * **Flexible Redemption**: Redeem different amounts based on usage
  </Accordion>

  <Accordion title="Time-Based Plans">
    Ideal for subscription models:

    * **Duration**: Set expiration time (days, months, years)
    * **Unlimited Usage**: Within the time period
    * **Auto-expiry**: Plan expires after duration
  </Accordion>

  <Accordion title="Hybrid Plans">
    Combine time and credits:

    * **Credits with Expiry**: E.g., 1000 credits valid for 30 days
    * **Rate Limiting**: Control usage within time periods
  </Accordion>
</AccordionGroup>

### Example Payment Plans

* **AI Travel Advisor**: Offer a "Regular" plan for $100/month or a "Premium" plan for $900/year.
* **Code Copilot**: A usage-based plan costing 10 USDC for 100 credits, with each request consuming 1 credit.
* **Legal Assistant**: A tiered model with a "Silver" plan (100 xDAI for 500 credits, 5-25 credits per query) and a "Gold" plan (1 ETH for unlimited credits for a year).

## How It All Works Together

<Steps>
  <Step title="Agent Registration">
    Builders register their AI agents with metadata and API endpoints, defining how the service can be accessed.
  </Step>

  <Step title="Plan Creation">
    Builders create one or more payment plans, setting prices, credit amounts, and consumption rules.
  </Step>

  <Step title="Subscriber Purchase">
    Users discover agents and purchase plans using crypto or fiat payments.
  </Step>

  <Step title="Access Token Generation">
    Upon purchase, subscribers receive bearer tokens for authenticated access.
  </Step>

  <Step title="Query & Validation">
    When querying an agent, the Nevermined Proxy validates the token and checks credit balance.
  </Step>

  <Step title="Automatic Billing">
    Credits are automatically deducted based on usage, with proof of consumption tracked on-chain.
  </Step>
</Steps>

By combining AI Agents with flexible Payment Plans, Nevermined empowers you to create sophisticated and scalable business models for your AI services.