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

> x402 Human Proof — differentiated pricing and spam protection for APIs serving humans and AI agents.

# Overview

## What is x402?

The x402 protocol lets any API accept per-request payments from humans and agents alike — but by itself it can't tell the two apart.

## x402 Human Proof

The **x402 Human Proof** extension solves that: it adds a human identity verification layer on top of x402, giving providers the signal they need to apply differentiated pricing and protect against bots, scalpers, and spam.

With Human Proof, providers can offer discounted tiers, free trials, or premium access to verified humans and the agents they control — while keeping standard rates for unverified traffic, or blocking it entirely. The result is sybil and spam resistance without giving up x402's open, permissionless model.

<Info>
  For agents consuming Human Proof–protected APIs, the [**Verified Agent Identity skill**](/agents/identity-overview) handles the human-proof flow automatically — no SDK integration needed.
</Info>

***

## Demo

<Card title="Try the Live Demo" icon="arrow-up-right-from-square" href="https://x402.billions.network/">
  x402.billions.network — claim a tile on the canvas using your agent
</Card>

The demo shows the full x402 Human Proof flow end-to-end: an agent visits a protected resource, handles a `402 Payment Required` response, proves it is operated by a verified human, pays for access, and mints a tile as an NFT on a shared canvas — all in a single conversation.

### How the demo works

<Steps>
  <Step title="Visit the demo and claim a tile">
    The user visits the x402 demo website and clicks **Claim Tiles**. A prompt is displayed that can be copied and passed directly to any agent.
  </Step>

  <Step title="Agent sets up its identity">
    The agent visits the server. If the Verified Agent Identity skill is not yet installed, it installs or updates it and sets up its decentralized identity automatically. The agent may present its DID to the user at this point.
  </Step>

  <Step title="Server returns HTTP 402">
    The agent requests a tile from the server. The server denies access with an HTTP `402 Payment Required` response — because the agent has not yet proven it is operated by a verified human and has not paid.
  </Step>

  <Step title="Agent presents verification and payment options">
    The agent surfaces both requirements to the user: a verification link to pair the human with the agent (via the Billions Web Wallet), and the available payment options. Both must be satisfied to access the resource — this is the combined power of x402 and the x402 Human Proof extension.
  </Step>

  <Step title="User pairs with the agent on-chain">
    The user opens the verification link in the Billions Web Wallet. They confirm their Proof of Uniqueness credential and complete the pairing. A permanent ownership attestation is created on-chain, linking the user to their agent.
  </Step>

  <Step title="User selects a payment option">
    With the pairing confirmed, the user selects their preferred payment option from the options the agent presented.
  </Step>

  <Step title="Agent pays, customises, and submits the tile">
    The agent handles the payment, customises the tile with the user's details, and submits it to the server.
  </Step>

  <Step title="Tile is minted as an NFT">
    The server mints the tile as an NFT and places it on the shared canvas. The agent confirms the tile details with the user.
  </Step>
</Steps>

***

## Server SDK

`@billionsnetwork/x402-human-proof-server` is built on top of x402 and lets service providers add human-proof verification to any API service. Offer better pricing and spam protection to verified humans — and the verified agents they control — without touching existing routes or payment logic.

**Features:**

* **Drop-in setup.** One function call; existing routes and payment logic stay unchanged.
* **Tiered pricing.** A discounted rate for verified humans and their agents, a standard rate for everyone else — claiming the discount requires valid proof.
* **Usage caps and shared quotas.** Hard per-human limits, enforced atomically, with multiple routes able to share one usage pool. If a payment fails after verification, the usage count rolls back automatically.
* **Credential gating.** Require any combination of credentials or skills per route, beyond "is this a human".

<Card title="Server SDK Reference" icon="server" href="/agents/server">
  Full reference for `@billionsnetwork/x402-human-proof-server`
</Card>

***

## Client SDK

`@billionsnetwork/x402-human-proof-client` enables any HTTP client or custom agent to authenticate against APIs protected by the x402 Human Proof Server SDK.

Most agents won't need this SDK directly. The [**Verified Agent Identity skill**](/agents/identity-overview) is a general-purpose identity skill that pairs a verified human to their agent and supports the x402 human-proof flow out of the box — install it and the agent can transact on human-proof protected APIs without any code changes.

Reach for the client SDK only when you're building a custom agent that needs direct control over the x402 flow or when you're building any other HTTP client that needs to prove a verified-human identity to a protected API with the Billions human-proof server SDK.

**Features:**

* **Automatic signing.** Verification challenges are signed in the background; nothing to wire up per request.
* **Smart tier selection.** Picks the best tier the client qualifies for, falling back to standard pricing when the discount isn't available.
* **Usage cap recovery.** Detects when the usage limit is hit and retries at standard pricing.
* **Works with any EVM wallet.**

<Card title="Client SDK Reference" icon="browser" href="/agents/client">
  Full reference for `@billionsnetwork/x402-human-proof-client`
</Card>