b402 — Private DeFi for AI Agents#

Shield. Swap. Lend. Bridge. All private. All gasless.

b402 wraps Railgun's ZK privacy pool with an agent-friendly SDK and MCP server. On-chain observers see "RelayAdapt called a DEX" — not your wallet, not your strategy.

Install#

bash

npx b402-mcp@latest --claude

This generates a wallet at ~/.b402/wallet.json, patches your Claude Desktop config, and registers the MCP server. Fund the wallet with USDC on Base to start.

Tools#

ToolWhat it doescheck_pool_balanceShow shielded balances, wallet state, vault positionsshield_usdcMove USDC into the Railgun privacy pool (gasless)private_swapSwap tokens inside the pool via ZK proof (USDC↔WETH, etc.)lend_privatelyDeposit into Morpho vault from pool (~4-8% APY)redeem_privatelyWithdraw from Morpho vault back to poolcross_chain_privatelyPrivate cross-chain transfer or swap via LI.FI (Base→Arb, etc.)get_swap_quotePreview swap rates without executingrun_strategyMulti-step: swap + lend + reserve in one call

Example prompts#

• "Check my privacy pool balance"
• "Shield 5 USDC into the pool"
• "Swap 2 USDC to WETH privately"
• "Privately send 1 USDC to 0xABC... on Arbitrum"
• "Private cross-chain swap: 1 USDC from pool to ARB on Arbitrum, to 0xABC..."
• "Lend 10 USDC in the steakhouse vault"
• "Run a yield strategy: 30% WETH, 50% lend, 20% reserve"

How it works#

text

Agent prompt → MCP tool call → b402-sdk
  → Railgun ZK proof (client-side, 10-30s)
  → RelayAdapt atomic tx (unshield → DeFi op → reshield)
  → On-chain: only RelayAdapt visible. No wallet linked.

Cross-chain: LI.FI routes through ~30 bridges + ~20 DEXes. Source and destination are unlinkable.

Supported chains#

ChainIDPrivacy poolCross-chainBase8453Yes (0% fee)Source + destArbitrum42161Yes (0% fee)Dest only (v1)BSC56Yes (0% fee)Dest only (v1)

SDK usage (for builders)#

typescript

import { B402 } from '@b402ai/sdk'

const b402 = new B402({ privateKey: process.env.WORKER_PRIVATE_KEY! })

// Shield into privacy pool (gasless)
await b402.shieldFromEOA({ token: 'USDC', amount: '10' })

// Private swap inside pool
await b402.privateSwap({ from: 'USDC', to: 'WETH', amount: '5' })

// Private cross-chain (LI.FI routing)
await b402.privateCrossChain({
  toChain: 'arbitrum',
  fromToken: 'USDC',
  toToken: 'ARB',
  amount: '1',
  destinationAddress: '0x...',
})

// Private lend (Morpho vaults, 4-8% APY)
await b402.privateLend({ amount: '10', vault: 'steakhouse' })

Links#

• SDK: npmjs.com/package/@b402ai/sdk
• MCP: npmjs.com/package/b402-mcp
• Starter: github.com/b402-ai/b402-starter
• Agent template: github.com/b402-ai/b402-agent-starter