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.For agents consuming Human Proof–protected APIs, the Verified Agent Identity skill handles the human-proof flow automatically — no SDK integration needed.
Demo
Try the Live Demo
x402.billions.network — claim a tile on the canvas using your agent
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
1
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.
2
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.
3
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.4
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.
5
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.
6
User selects a payment option
With the pairing confirmed, the user selects their preferred payment option from the options the agent presented.
7
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.
8
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.
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”.
Server SDK Reference
Full reference for
@billionsnetwork/x402-human-proof-serverClient 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 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.
Client SDK Reference
Full reference for
@billionsnetwork/x402-human-proof-client