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

# Core Concepts

> Learn how Nevermined adds payments and access control to AI agents, MCP tools, and static assets with payment plans, metering, and per-request entitlement.

Nevermined adds a payment and entitlement layer to any **monetizable service** (agent APIs, MCP tools, or static assets). Attach a **payment plan** and each inbound request is validated, metered, and settled in real time. No checkout flows, no manual invoicing, no distinction between human and agent callers.

## What Can You Monetize?

Nevermined validates each inbound request against the caller’s entitlement before your code runs:

* **Agent APIs** - AI agents exposed as HTTP endpoints (REST, webhooks, etc.)
* **MCP Tools** - tool endpoints served via the Model Context Protocol
* **Static Assets** - gated resources like files, datasets, or downloads

Every monetizable service has:

* A **public endpoint** (the URL callers hit)
* A **payment plan** (pricing and access terms)
* A **validation step** (Nevermined checks entitlement per request)
* **Usage tracking** (automatic metering on every call)

## Standards and protocols (x402)

Nevermined supports modern payment standards used in agentic commerce. In particular, **x402** standardizes how clients and servers negotiate payment-required requests, enabling smoother, interoperable monetization flows.

If you're integrating with x402-compatible clients/servers, see the [x402 integration](/docs/development-guide/nevermined-x402).

## What is a Payment Plan?

A payment plan defines how users pay and what they're entitled to consume:

<CardGroup cols={2}>
  <Card title="Payment Method" icon="credit-card">
    [**Cards**](/docs/products/payments/overview) (Visa, Stripe, or Braintree) or [**Crypto**](/docs/integrate/patterns/stablecoin-payments) (USDC, EURC on-chain).
  </Card>

  <Card title="Pricing Model" icon="sack-dollar">
    **Fixed** (same cost per call) or **Dynamic** (builder-defined per request, or cost+margin).
  </Card>

  <Card title="Plan Type" icon="calendar-days">
    **Prepaid** (buy upfront) or **Pay-as-you-go** (charge per request).
  </Card>

  <Card title="Payouts" icon="building-columns">
    Merchants receive fiat payouts via [Stripe Connect](https://stripe.com/connect) or crypto directly to their wallet. Connect your account in the [Nevermined App](https://nevermined.app).
  </Card>
</CardGroup>

<AccordionGroup>
  <Accordion title="Prepaid plans">
    Users buy a plan upfront. Each API call deducts from their balance:

    * **Fixed pricing**: every request costs the same (e.g., \$10 for 100 requests at \$0.10 each)
    * **Dynamic pricing**: charge different amounts per request based on complexity, or apply cost+margin automatically
  </Accordion>

  <Accordion title="Pay-as-you-go">
    No upfront purchase. Charge the user's card or wallet on each request:

    * **Cards**: agents charge via [card delegation](/docs/products/payments/overview)
    * **Crypto**: settle in USDC or EURC on-chain
  </Accordion>

  <Accordion title="Time-limited plans">
    Add expiration to any plan:

    * **Duration**: set expiry (days, months, years)
    * **Hybrid**: combine usage limits with time limits (e.g., 1,000 requests valid for 30 days)
  </Accordion>

  <Accordion title="Outcome-based pricing">
    Charge on success: meetings booked, leads qualified, issues resolved. Only bill when your agent delivers a defined outcome or milestone.
  </Accordion>
</AccordionGroup>

### Examples

* **Customer Support Agent**: \$49/month unlimited, or \$10 for 1,000 calls
* **Dataset Access**: \$99 for 30-day access
* **Agent API**: \$0.10/call prepaid, or \$0.15/call PAYG
* **Sales Agent**: \$5 per qualified lead (outcome-based)

## How It All Works Together

<Steps>
  <Step title="Register your API">
    Define your service interface and metadata using the Payments SDK.
  </Step>

  <Step title="Create a payment plan">
    Set payment method, pricing model, and plan type using the Payments SDK.
  </Step>

  <Step title="Users or agents purchase access">
    Purchase a prepaid or pay-as-you-go plan, paid with [card](/docs/products/payments/overview) or crypto.
  </Step>

  <Step title="Validate before delivery">
    Validate entitlement before serving requests or granting access.
  </Step>

  <Step title="Track and settle">
    Automatically track usage per request and settle payments.
  </Step>
</Steps>

## Payment Methods

<CardGroup cols={2}>
  <Card title="Cards" icon="credit-card" href="/docs/products/payments/overview">
    Pay with real Visa, Stripe, or Braintree cards via [card delegation](/docs/products/payments/overview). Agents charge against spending delegations with lifetime limits, usage caps, and (for Visa) per-delegation WebAuthn/passkey device binding. No crypto wallet needed.
  </Card>

  <Card title="Crypto" icon="coins" href="/docs/integrate/patterns/stablecoin-payments">
    USDC, EURC, or any ERC-20 token on-chain. Lowest fees and full transparency for crypto-native users.
  </Card>
</CardGroup>

### Fiat vs crypto: what each plan needs

A plan is paid for in **one** of two ways — fiat (card) or crypto — and each needs different setup before you can pay. A plan is never both. Check the type up front, so you don't enroll a card for a crypto plan or try to pay a card plan from a wallet:

|                          | **Fiat plan** (`nvm:card-delegation`)                                                 | **Crypto plan** (`nvm:erc4337`)              |
| ------------------------ | ------------------------------------------------------------------------------------- | -------------------------------------------- |
| **What the buyer needs** | An enrolled card with the plan's provider                                             | A smart account funded with the plan's token |
| **Set up**               | [Enroll a card](/docs/products/payments/card-enrollment) — Stripe, Braintree, or Visa | Fund the account with USDC / EURC            |
| **Delegation**           | `provider: 'stripe'` (or `braintree` / `visa`), `currency: 'usd'`                     | `provider: 'erc4337'`, `currency: 'usdc'`    |
| **Token scheme**         | pass `scheme: 'nvm:card-delegation'`                                                  | `scheme: 'nvm:erc4337'` (the default)        |
| **Detect in code**       | `resolveScheme()` / `resolve_scheme()` → `nvm:card-delegation`                        | → `nvm:erc4337`                              |

Not sure which a plan uses? See [Which payment type does this plan need?](/docs/development-guide/order-plans#which-payment-type-does-this-plan-need) to detect it in code before you pay.

## Merchant Onboarding

<CardGroup cols={2}>
  <Card title="Payouts" icon="building-columns">
    Merchants receive fiat payouts via [Stripe Connect](https://stripe.com/connect) or crypto directly to their wallet. Connect your account in the [Nevermined App](https://nevermined.app).
  </Card>

  <Card title="Security & Compliance" icon="shield-check">
    ISO 27001, SOC 2 Type II, PCI SAQ-D, GDPR compliant. Card data captured via PCI Level 1 infrastructure (VGS). Nevermined never stores raw card numbers.
  </Card>
</CardGroup>

## Next steps

Building an **AI agent that needs to pay** for services? Follow [AI Agents: Buy Access Autonomously](/docs/getting-started/ai-agent-purchase) — get an API key, enroll a card, delegate a budget, and make an x402 purchase end to end.