What is x402?

x402 is an open protocol for machine-to-machine payments over HTTP. When an API returns 402 Payment Required, it includes payment instructions. The client pays (USDC on Solana, Base, or other chains), and the API delivers the response. No API keys, no subscriptions, no invoices. Dexter operates the most-used x402 facilitator, processing millions of settlements.

Install

npx @dexterai/opendexter install

Supports Cursor, Claude Code, Codex, VS Code, Windsurf, and Gemini CLI.

The installer creates a local Solana wallet at ~/.dexterai-mcp/wallet.json and writes the MCP config for your client. Fund the wallet with USDC and your agent can start paying for APIs from your own machine.

Manual Configuration

Cursor — ~/.cursor/mcp.json:

{
  "mcpServers": {
    "dexter-x402": {
      "command": "npx",
      "args": ["-y", "@dexterai/opendexter@latest"]
    }
  }
}

Claude Code:

claude mcp add dexter-x402 -- npx -y @dexterai/opendexter@latest

Codex — ~/.codex/config.toml:

[mcp_servers.dexter-x402]
command = "npx"
args = ["-y", "@dexterai/opendexter@latest"]

Tools

x402_search

Search the Dexter Marketplace for paid API resources. Returns pricing, quality scores, verification status, seller reputation, and call volume.

"Find image generation APIs under $0.10"
→ x402_search(query: "image generation", maxPriceUsdc: 0.10)

"What DeFi tools are available on Solana?"
→ x402_search(category: "DeFi", network: "solana")

| Param | Type | Description | |-------|------|-------------| | query | string | Search term | | category | string | "AI", "DeFi", "Data", "Tools", "Games", "Creative" | | network | string | "solana", "base", "polygon" | | maxPriceUsdc | number | Maximum price per call | | verifiedOnly | boolean | Only quality-checked endpoints | | sort | string | "marketplace" (default) "relevance" "quality_score" "settlements" "volume" "recent" | | limit | number | 1–50, default 20 |

x402_fetch

Call any x402-protected API with automatic payment. The MCP detects the 402 response, signs a USDC payment with your local wallet, and retries the request — returning the API response directly.

Works with any x402 seller, not just Dexter endpoints:

"Get a Jupiter DEX quote for 1 SOL to USDC"
→ x402_fetch("https://x402.dexter.cash/api/jupiter/quote?inputMint=So11...&amount=1000000000")
→ Pays $0.05, returns the full quote with route plan

"Generate an image of a robot trading crypto"
→ x402_fetch("https://api.xona-agent.com/image-model/seedream-4.5", method: "POST", body: '{"prompt":"a robot trading crypto"}')
→ Pays $0.08 to Xona Agent, returns the image URL

| Param | Type | Description | |-------|------|-------------| | url | string | The x402 resource URL | | method | string | GET POST PUT DELETE — default GET | | body | string | JSON request body for POST/PUT |

Response includes the API data plus on-chain settlement proof:

{
  "status": 200,
  "data": { "...API response..." },
  "payment": {
    "settled": true,
    "details": {
      "transaction": "Djo6aA9SXFx...",
      "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
      "payer": "2SB3VTnjrct..."
    }
  }
}

x402_pay

Alias of x402_fetch for clients that want an explicit payment verb.

Use it when you want the model or user flow to think in terms of:

1. discover
2. inspect
3. pay and call

The request schema and settlement behavior are the same as x402_fetch.

x402_check

Probe an endpoint to see its pricing and payment options without spending anything. Returns the full 402 requirements including price per chain, accepted assets, and input/output schemas when available.

"How much does this API cost?"
→ x402_check("https://x402.dexter.cash/api/v2-test", method: "POST")
→ $0.01 USDC on Solana, $0.01 USDC on Base

| Param | Type | Description | |-------|------|-------------| | url | string | The URL to check | | method | string | GET POST PUT DELETE — default GET |

x402_wallet

Show wallet addresses (Solana + EVM), USDC balances across all supported chains, and deposit instructions. If the wallet has no USDC, returns funding tips.

{
  "address": "2SB3VTnjrct9ayYCsQ4Fi5C5vNVpwL8X8RYUQoaPNZGh",
  "solanaAddress": "2SB3VTnjrct9ayYCsQ4Fi5C5vNVpwL8X8RYUQoaPNZGh",
  "evmAddress": "0x1234...abcd",
  "network": "multichain",
  "chainBalances": {
    "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp": { "available": "940000", "name": "Solana", "tier": "first" },
    "eip155:8453": { "available": "0", "name": "Base", "tier": "first" }
  },
  "balances": { "usdc": 0.94, "fundedAtomic": "940000", "availableAtomic": "940000" },
  "supportedNetworks": ["solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp", "eip155:8453", "eip155:137", "eip155:42161", "eip155:10", "eip155:43114"],
  "walletFile": "~/.dexterai-mcp/wallet.json"
}

CLI

Every tool is also available as a standalone command:

npx @dexterai/opendexter wallet
npx @dexterai/opendexter search "token analysis"
npx @dexterai/opendexter fetch "https://x402.dexter.cash/api/v2-test" --method POST

Wallet

A dual Solana + EVM wallet stored at ~/.dexterai-mcp/wallet.json with 600 permissions. Private keys never leave your machine.

Override with environment variables:

export DEXTER_PRIVATE_KEY="your-solana-base58-private-key"
export EVM_PRIVATE_KEY="0x-prefixed-hex-private-key"

SOLANA_PRIVATE_KEY is also accepted for the Solana key. Env vars take priority over the wallet file. Existing Solana-only wallet files are automatically upgraded with an EVM keypair on first load.

Payment Model

@dexterai/opendexter is the local-wallet OpenDexter surface:

• transport: local stdio MCP server
• signer: dual Solana + EVM wallet file, or DEXTER_PRIVATE_KEY / EVM_PRIVATE_KEY env vars
• chains: Solana, Base, Polygon, Arbitrum, Optimism, Avalanche
• best for: Cursor, Codex, Claude Code, CLI agents, and local workflows

If you want a no-install hosted flow with session wallets, use OpenDexter MCP at https://open.dexter.cash/mcp.

Supported Chains

| Chain | Network ID | Local signing status | |-------|------------|----------------------| | Solana | solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp | Local wallet signing + balance queries | | Base | eip155:8453 | Local wallet signing + balance queries | | Polygon | eip155:137 | Local wallet signing + balance queries | | Arbitrum | eip155:42161 | Local wallet signing + balance queries | | Optimism | eip155:10 | Local wallet signing + balance queries | | Avalanche | eip155:43114 | Local wallet signing + balance queries |

The local wallet generates both a Solana keypair and an EVM private key. @dexterai/x402 handles chain detection and signing automatically — when a 402 response specifies an EVM chain, the SDK signs with your EVM key; for Solana endpoints, it signs with the Solana keypair.

Links

• Dexter Marketplace
• Dexter Facilitator
• @dexterai/x402 SDK
• x402 Protocol
• Twitter
• Telegram
• Become a Seller

License

MIT