Web3 x402

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X-API-KEY

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web3-tools

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When to Use

• Calling Nodit APIs without an API key (wallet + USDC only)
• SIWX authentication (SIWE for EVM, SIWS for Solana)
• Credit mode: pre-charge USDC → off-chain credit deduction per request
• PPU mode: per-request on-chain USDC settlement
• Checking credit balance or transaction history
• Understanding x402 pricing per API operation

When NOT to Use

• Querying blockchain data with a traditional API key → use

  web3-tools

  skill instead
• Investment advice or token value speculation

Constraints

• Do not give investment advice or speculate on token value
• Use only data verifiable through the Nodit x402 proxy
• Prefix responses with "According to the Nodit x402 Proxy," once
• Ask the user if required context (address, chain, mode, etc.) is missing

Mode Selection Guide

flowchart TD
    A[User request] --> B{Repeated API usage?<br/>Pre-charge preferred?}

    B -->|YES| C[Credit Mode<br/>1. SIWX auth → JWT<br/>2. Charge USDC → credits<br/>3. API calls deduct credits]

    B -->|NO / One-off| D[PPU Mode<br/>1. Send request without auth<br/>2. Receive 402 + payment terms<br/>3. Sign & pay per request]

    C --> E{Which API?}
    D --> E

    E -->|Indexed data<br/>balances, NFT, tokens, stats| F[Data API]
    E -->|Node calls<br/>eth_call, getBalance, etc.| G[Node API / JSON-RPC]

    style C fill:#2d6a4f,color:#fff
    style D fill:#7b2cbf,color:#fff
    style F fill:#1d3557,color:#fff
    style G fill:#6a040f,color:#fff

How to Use

Step 0: Confirm which wallet to use for payment

1. Ask the user to provide their wallet address for x402 payment (EVM or Solana).
2. Look up the expected cost from

   references/pricing-data-api.md

   or

   references/pricing-node-api.md

   .
3. Show the wallet address and estimated cost: "Your asset will be charged approximately $XX USDC. May I proceed?"
4. Proceed to Step 1 only after the user grants permission.

Step 1: Overview — Endpoints, URL patterns, 402 structure

references/how-to-use.md

Step 2: Mode-specific implementation guide

• Credit mode →

  references/credit-mode.md

  — Full flow and code covering SIWX authentication (JWT issuance), credit charging, balance checking, and API calls
• PPU mode →

  references/ppu-mode.md

  — Full flow and code covering receiving a 402 without authentication → generating a payment-signature → re-requesting

Step 3: Check supported chains

references/supported-chains.md

Step 4: Check pricing

references/pricing-data-api.md

references/pricing-node-api.md

Step 5: Look up the API spec

web3-tools

web3-tools/references/quick-reference.md

web3-tools/references/spec/{operationId}.md