> ## Documentation Index > Fetch the complete documentation index at: https://veniceai-joshua-mo-143-feat-copy-to-markdown-button.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # X402 Top Up > Top up your Venice credit balance using an `X-402-Payment` header. If the header is missing, the endpoint returns payment requirements. This is the primary x402 payment endpoint. It currently returns Base and Solana USDC payment options in the `accepts` array. All inference endpoints (chat, image, audio, video) consume from the credit balance you establish here. ## OpenAPI ````yaml POST /x402/top-up openapi: 3.0.0 info: description: The Venice.ai API. termsOfService: https://venice.ai/legal/tos title: Venice.ai API version: '20260606.183624' x-guidance: >- Venice.ai is an OpenAI-compatible inference API supporting text, image, audio, and video generation. **Authentication options:** - API Key: Use Bearer token in Authorization header - x402 Wallet: Use USDC credits via EVM or Solana wallet (no account required) **For x402 wallet access:** 1. POST /x402/top-up without headers to get payment requirements 2. Choose one of the returned Base or Solana payment options and sign a USDC payment using the x402 SDK 3. POST /x402/top-up with X-402-Payment header to add credits 4. Call any inference endpoint with X-Sign-In-With-X header **Pricing:** Prepaid credits consumed per request. Check /models for available models and their capabilities. servers: - url: https://api.venice.ai/api/v1 security: - BearerAuth: [] tags: - description: >- Generate speech/audio, transcribe audio, and manage asynchronous audio generation jobs. name: Audio - description: >- Given a list of messages comprising a conversation, the model will return a response. Supports multimodal inputs including text, images, audio (input_audio), and video (video_url) for compatible models. name: Chat - description: List and describe the various models available in the API. name: Models - description: Generate and manipulate images using AI models. name: Image - description: Generate videos using AI models. name: Video - description: List and retrieve character information for use in completions. name: Characters - description: >- Billing and usage analytics. **Beta**: This API is currently in beta and may be unstable. Endpoints, request/response schemas, and behavior may change without notice. name: Billing - description: Proxy JSON-RPC requests to blockchain nodes. Billed per credit. name: Crypto RPC - description: >- Wallet-based API access using the x402 protocol. No API key required — authenticate with an EVM or Solana wallet. **How it works:** 1. **Authenticate** — Send an `X-Sign-In-With-X` header (base64-encoded signed SIWX payload) with any request. EVM wallets sign an EIP-4361 SIWE message; Solana wallets sign the Solana SIWX message with Ed25519. See the `siwx` security scheme for the exact format. 2. **Top up** — `POST /x402/top-up` without a payment header returns an `accepts` array with Base and Solana USDC payment options. Choose one entry, sign it using the x402 SDK (`npm install x402`), and re-submit with the `X-402-Payment` header. 3. **Use any endpoint** — All inference endpoints (chat, image, audio, video, embeddings) accept `siwx` as an alternative to `BearerAuth`. Charges are deducted from your USDC credit balance. 4. **Monitor balance** — `GET /x402/balance/{walletAddress}` returns your current balance. The `X-Balance-Remaining` response header on inference calls also reports it. **Quick start (5 lines):** ``` import { VeniceClient } from '@venice-ai/x402-client' const venice = new VeniceClient(process.env.WALLET_KEY) await venice.topUp(10) // $10 USDC on a supported x402 rail const res = await venice.chat({ model: 'zai-org-glm-5-1', messages: [{ role: 'user', content: 'Hello!' }] }) ``` **Payment:** USDC on Base (chain ID 8453) or Solana mainnet. Minimum top-up: $5. Alternatively, stake DIEM tokens for daily credits (1 DIEM = $1/day). name: x402 externalDocs: description: Venice.ai API documentation url: https://docs.venice.ai paths: /x402/top-up: post: tags: - x402 summary: /api/v1/x402/top-up description: >- Top up your Venice credit balance using an `X-402-Payment` header. If the header is missing, the endpoint returns payment requirements. This is the primary x402 payment endpoint. It currently returns Base and Solana USDC payment options in the `accepts` array. All inference endpoints (chat, image, audio, video) consume from the credit balance you establish here. operationId: topUpX402Balance parameters: - description: >- Signed x402 payment payload used to top up the wallet balance on a supported rail such as Base or Solana. in: header name: X-402-Payment required: false schema: example: eyJ4NDAyVmVyc2lvbiI6MiwicGF5bG9hZCI6Ii4uLiJ9 type: string requestBody: description: >- No JSON body required. Payment is sent via the X-402-Payment header. Send an empty POST to discover payment requirements. required: false content: application/json: schema: type: object properties: {} responses: '200': description: Top-up completed successfully. content: application/json: schema: type: object properties: success: type: boolean enum: - true data: type: object properties: walletAddress: type: string description: Wallet that received the credited balance. example: 0xyour_wallet_address amountCredited: type: number description: Amount credited to the wallet in USD. example: 10 newBalance: type: number description: Updated wallet balance in USD after the top-up. example: 22.5 paymentId: type: string description: Unique identifier for the x402 payment. example: payment_01HZY8M4W4Y6QZ8B6Q4P0V3J2K required: - walletAddress - amountCredited - newBalance - paymentId additionalProperties: false required: - success - data additionalProperties: false '400': description: Invalid request parameters content: application/json: schema: type: object properties: error: type: string description: Machine-readable x402 error code. example: X402_INVALID_PAYMENT message: type: string description: Human-readable description of the x402 failure. example: Invalid payment header details: type: object properties: {} description: Optional structured details about the x402 error. example: reason: signature_mismatch required: - error - message additionalProperties: false '402': description: Payment information required before the top-up can be processed. content: application/json: schema: type: object properties: x402Version: type: number description: x402 protocol version. example: 2 accepts: type: array items: type: object properties: protocol: type: string enum: - x402 description: Payment protocol identifier. version: type: number description: Protocol version. example: 2 network: type: string description: >- Payment network. Base uses CAIP-2 EIP-155 format; Solana uses the x402 Solana network alias. example: solana asset: type: string description: USDC token address or mint for the selected network. example: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v amount: type: string description: >- Minimum payment amount in base units (USDC has 6 decimals). example: '5000000' payTo: type: string description: Receiver wallet address. example: 8qUL23aSj7mDWdoLMXGHFvnVCT9wd7jXcysiekroADEL extra: type: object properties: {} description: >- Network-specific x402 metadata. Solana accepts include a feePayer. example: name: USD Coin version: '2' feePayer: BFK9TLC3edb13K6v4YyH3DwPb5DSUpkWvb7XnqCL9b4F required: - protocol - version - network - asset - amount - payTo additionalProperties: false description: Array of accepted payment options. required: - x402Version - accepts additionalProperties: false '429': description: Rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/StandardError' '500': description: An unknown error occurred content: application/json: schema: type: object properties: error: type: string description: Machine-readable x402 error code. example: X402_INVALID_PAYMENT message: type: string description: Human-readable description of the x402 failure. example: Invalid payment header details: type: object properties: {} description: Optional structured details about the x402 error. example: reason: signature_mismatch required: - error - message additionalProperties: false security: [] components: schemas: StandardError: type: object properties: error: type: string description: A description of the error required: - error securitySchemes: BearerAuth: bearerFormat: JWT scheme: bearer type: http ````