Non-custodial token swap on Base via Permit2, paid per-call with x402 USDC micropayments.
What it does
The Silverback `/api/v1/swap` endpoint executes non-custodial token swaps on Base (chain ID 8453) using the Permit2 mechanism. Rather than executing the swap directly, it returns EIP-712 Permit2 signing data that the caller signs and broadcasts themselves, keeping full custody of funds. The endpoint accepts a wallet address, input/output token identifiers (symbols like USDC/WETH or 0x contract addresses), a human-readable amount, and an optional slippage parameter.
This endpoint is part of the Silverback x402 DeFi Intelligence API, which offers 11 pay-per-use endpoints covering swap execution, technical analysis, yield intelligence, arbitrage scanning, token audits, whale tracking, portfolio views, pool analysis, and more. All endpoints use the x402 micropayment protocol — callers receive a 402 Payment Required challenge, sign a USDC authorization, and resend with payment proof. The swap endpoint is priced at $0.05 per call (the highest tier), while other endpoints range from $0.01 to $0.03. Payments settle in USDC on Base, Solana, or SKALE, with a 15% discount available when paying with the $BACK token via Permit2 on Base.
The API is live and returns a 402 challenge on unauthenticated POST requests. The OpenAPI 3.1.0 spec is well-documented with full request schemas. However, response schemas are not detailed beyond summary descriptions, and the external docs link at docs.silverbackdefi.app was not crawlable during probing.
Capabilities
Use cases
- —AI agents autonomously swapping tokens on Base without custodial risk
- —Building automated trading strategies that pay per swap execution
- —Integrating non-custodial swap functionality into wallets or dashboards via micropayments
- —Agent-driven portfolio rebalancing using Permit2 signing data
Fit
Best for
- —Autonomous AI agents needing on-chain swap execution on Base
- —Developers wanting pay-per-use non-custodial swap infrastructure
- —Applications that need EIP-712 Permit2 signing payloads without managing swap routing
Not for
- —Users needing direct swap execution (this returns signing data, not a completed transaction)
- —Swaps on chains other than Base (use jupiter-quote endpoint for Solana)
- —Free or subscription-based swap APIs
Quick start
curl -X POST https://silverback-x402.onrender.com/api/v1/swap \
-H "Content-Type: application/json" \
-d '{
"walletAddress": "0xYourWalletAddress",
"tokenIn": "USDC",
"tokenOut": "WETH",
"amountIn": "100",
"slippage": "1"
}'Example
Request
{
"tokenIn": "USDC",
"amountIn": "100",
"slippage": "1",
"tokenOut": "WETH",
"walletAddress": "0x1234567890abcdef1234567890abcdef12345678"
}Endpoint
Quality
Full OpenAPI 3.1.0 schema with clear request parameters, pricing info, and guidance. The endpoint is live (402 challenge confirmed). Response schema details and external docs are missing, preventing a higher score.
Warnings
- —Response schema not documented — only a summary description is provided for 200 responses.
- —External docs at docs.silverbackdefi.app were not reachable during crawl.
- —The 402 challenge object was empty in the probe, so exact payment parameters (token address, amount in base units) could not be independently verified from the wire challenge.
- —This endpoint returns signing data only — the caller must sign and broadcast the transaction themselves.
Citations
- —The swap endpoint is priced at $0.05 per callhttps://silverback-x402.onrender.com
- —Non-custodial token swap on Base returning EIP-712 Permit2 signing datahttps://silverback-x402.onrender.com
- —11 pay-per-use endpoints via x402 micropayments, USDC on Base, Solana, and SKALEhttps://silverback-x402.onrender.com
- —15% discount available when paying with $BACK token via Permit2 on Basehttps://silverback-x402.onrender.com
- —Endpoint returns 402 Payment Required on unauthenticated POSThttps://silverback-x402.onrender.com