X402 Client Documentation

JumpGate offers a pay-per-use AI inference API powered by the x402 payment protocol. No API keys, no accounts, no pre-deposits—just send a request and pay automatically with USDC.

Endpoint: https://jumpgate.ambient.xyz/paid/chat

What makes this different:

🔐 No authentication required - No API keys or registration
💰 Pay-per-request - Only pay for what you use
⚡ Instant payments - USDC transactions on Solana or Base
🌐 Multi-chain support - Pay with Solana mainnet or Base mainnet USDC
🤖 Agent-friendly - Perfect for AI agents that need to pay for services autonomously
📊 Transparent pricing - Cost calculated upfront based on token usage

Supported Payment Networks

JumpGate accepts USDC payments on two networks:

Network	Chain ID	Token	Recommended For
Solana Mainnet	`solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp`	USDC	Low fees, fast finality, high throughput
Base Mainnet	`eip155:8453`	USDC	Ethereum ecosystem, EVM compatibility

How x402 Payment Protocol Works

The x402 protocol brings cryptocurrency payments to standard HTTP requests using the 402 Payment Required status code.

Payment Flow

1. Client → Server: POST /paid/chat (no payment)
2. Server → Client: 402 Payment Required + payment options (Solana + Base)
3. Client: Selects preferred chain and creates on-chain payment
4. Client → Facilitator: Submits payment proof
5. Facilitator → Client: Issues payment token
6. Client → Server: Retries request with X-Payment header
7. Server: Verifies payment with facilitator
8. Server → Client: 200 OK + streaming inference response

The good news: Client libraries handle steps 3-6 automatically! You just make a normal HTTP request.

Key Components

Client: Your application making the inference request
Server: JumpGate relayer (jumpgate.ambient.xyz)
Facilitator: PayAI Network service that verifies payments
Blockchain: Solana mainnet or Base mainnet for USDC payments

Pricing

JumpGate uses a transparent token-based pricing model:

Resource	Price
Input tokens	`PRICE_PER_INPUT_TOKENS` micro-USDC per token
Output tokens	`PRICE_PER_OUTPUT_TOKENS` micro-USDC per token

Total cost calculation:

cost = (input_tokens × PRICE_PER_INPUT_TOKENS) + (output_tokens × PRICE_PER_OUTPUT_TOKENS)

💡 Pricing details: Visit https://app.ambient.xyz/billing

Note on HTTP 403 Responses: Very small USDC payment amounts (particularly with x402 payments) may result in HTTP 403 Forbidden responses. This is due to minimum payment thresholds imposed by the payment processing network. If you encounter a 403 response, try increasing the payment amount slightly.

Cost Estimation

Before making a request, you can estimate the cost:

Input tokens: Count the characters in your prompt (approximately 1 token = 1 byte)
Output tokens: Set max_completion_tokens to your desired maximum
Calculate: total_cost = input_cost + output_cost

Tip: Add a small buffer (e.g., +50 micro-USDC) to account for price variations.

Network Fee Comparison

Network	Avg. Transaction Fee	Finality
Solana	~$0.00001	~400ms
Base	~$0.01-0.05	~2 seconds

Prerequisites

Before you start, you'll need:

Option A: Solana (Recommended)

Solana Wallet: A keypair with SOL and USDC on mainnet
- Generate: solana-keygen new
- Get SOL: Purchase from exchange or bridge
- Get USDC: Purchase from exchange or bridge
Solana RPC Access:
- Public mainnet: https://api.mainnet-beta.solana.com
- Recommended: Use a paid RPC provider (Helius, QuickNode, Alchemy)

Option B: Base

Ethereum Wallet: Private key with ETH and USDC on Base mainnet
- Use MetaMask, Rainbow, or any Ethereum wallet
- Bridge ETH to Base for gas fees
- Bridge or purchase USDC on Base
Base RPC Access:
- Public: https://mainnet.base.org
- Recommended: Use Alchemy, Infura, or QuickNode

Overview

Developers

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