{"id":"d5b8fa57-5ca5-4f93-a32c-e4a545d81d34","shortId":"RRXSY3","kind":"x402","title":"Non-custodial token swap on Base via Permit2, paid per-call with x402 USDC micropayments.","tagline":"Non-custodial token swap on Base via Permit2, paid per-call with x402 USDC micropayments.","description":"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.\n\nThis 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.\n\nThe 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.","tags":[],"capabilities":["token-swap","permit2-signing-data","eip-712","non-custodial-execution","base-chain","x402-micropayments","usdc-payment","defi-execution","slippage-control"],"categories":["defi","crypto","swap"],"synonyms":["token swap API","DEX swap","Permit2 swap","Base chain swap","USDC swap","non-custodial swap","EIP-712 swap","agent DeFi swap","x402 swap"],"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."],"endpointUrl":"https://silverback-x402.onrender.com/api/v1/swap","protocol":"x402","transport":"http","auth":{"type":"x402","details":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0xD34411a70EffbDd000c529bbF572082ffDcF1794","amount":"50000","scheme":"exact","network":"eip155:8453","maxTimeoutSeconds":300},{"asset":"EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v","extra":{"feePayer":"8wLKe8H59eni5DmERU27GiRHGnN9fogRoq9yNqyKKNJA"},"payTo":"4HVvnhyXTkMnPbMBo9r3kfvYhzW4JSbLGdXg9SkUcVSe","amount":"50000","scheme":"exact","network":"solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp","maxTimeoutSeconds":300},{"asset":"0x85889c8c714505E0c94b30fcfcF64fE3Ac8FCb20","extra":{"name":"USD Coin","version":"1"},"payTo":"0xD34411a70EffbDd000c529bbF572082ffDcF1794","amount":"50000","scheme":"exact","network":"eip155:1187947933","maxTimeoutSeconds":300},{"asset":"USDC","extra":{"symbol":"USDC","nodeUrl":"https://api.keeta.com","decimals":6,"serverAddress":"keeta_aabwgiqyij4scwktdoczzvhpi33btieeses5sezeqzqmpi5ik76ttyegwuvfsai","permissionSetupUrl":"/api/v1/keeta/setup-permission"},"payTo":"keeta_aabaolle2k3hceayy4vkyw7smgl35o5wbqeebt2fibyx5sxxodneqb2rmwqkjci","amount":"50000","scheme":"keeta-usdc","network":"keeta:main","expiresAt":1771370264672,"paymentId":"3e0496ed-02cb-4568-8386-ab71bd046200","amountHuman":"0.050000","description":"Token swap via 0x Permit2. You sign EIP-712 data, append signature to tx, and broadcast. Response includes step-by-step instructions with code examples.","tokenAddress":"keeta_amnkge74xitii5dsobstldatv3irmyimujfjotftx7plaaaseam4bntb7wnna","maxTimeoutSeconds":300,"requiresPermission":true}]},"qualityScore":"0.720","qualityRationale":"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 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'/api/v1/swap':37 '0.01':183 '0.03':185 '0.05':172 '0x':92 '11':118 '15':197 '3.1.0':225 '402':153,217 '8453':49 'Base chain swap' 'DEX swap' 'EIP-712 swap' 'Permit2 swap' 'USDC swap' 'accept':81 'address':84,94 'agent DeFi swap' 'amount':99 'analysi':128,140 'api':115,211 'arbitrag':131 'audit':134 'author':160 'avail':199 'back':204 'base':7,24,46,191,209 'base-chain' 'beyond':241 'broadcast':72 'call':13,30,174 'caller':69,150 'chain':47 'challeng':156,218 'contract':93 'cover':124 'crawlabl':253 'custodi':3,20,42,76 'data':66 'defi':113 'defi-execution' 'descript':243 'detail':240 'direct':59 'discount':198 'doc':247 'docs.silverbackdefi.app':250 'document':230 'eip':62 'eip-712' 'endpoint':38,80,106,123,144,168,180 'execut':39,56,126 'extern':246 'full':75,232 'fund':78 'highest':176 'howev':235 'human':97 'human-read':96 'id':48 'identifi':87 'input/output':85 'intellig':114,130 'keep':74 'like':89 'link':248 'live':213 'mechan':53 'micropay':17,34,148 'non':2,19,41 'non-custodi':1,18,40 'non-custodial swap' 'non-custodial-execution' 'offer':117 'openapi':224 'option':102 'paid':10,27 'paramet':104 'part':108 'pay':120,201 'pay-per-us':119 'payment':154,164,186 'per':12,29,121,173 'per-cal':11,28 'permit2':9,26,52,64,207 'permit2-signing-data' 'pool':139 'portfolio':137 'post':221 'price':170 'probe':255 'proof':165 'protocol':149 'rang':181 'rather':54 'readabl':98 'receiv':151 'request':222,233 'requir':155 'resend':162 'respons':236 'return':61,215 'scan':132 'schema':234,237 'settl':187 'sign':65,70,157 'silverback':36,111 'skale':194 'slippag':103 'slippage-control' 'solana':192 'spec':226 'summari':242 'swap':5,22,44,58,125,167 'symbol':88 'technic':127 'tier':177 'token':4,21,43,86,133,205 'token swap API' 'token-swap' 'track':136 'unauthent':220 'usdc':16,33,159,189 'usdc-payment' 'usdc/weth':90 'use':50,122,145 'via':8,25,206 'view':138 'wallet':83 'well':229 'well-docu':228 'whale':135 'x402':15,32,112,147 'x402 swap' 'x402-micropayments' 'yield':129","prices":[{"id":"158b824f-eafd-4d25-82f6-aff71d34c933","listingId":"d5b8fa57-5ca5-4f93-a32c-e4a545d81d34","amountUsd":null,"unit":"per_call","nativeCurrency":"USD COIN","nativeAmount":null,"chain":"base","payTo":"0xD34411a70EffbDd000c529bbF572082ffDcF1794","paymentMethod":"x402-usd coin","isPrimary":true,"details":{"scheme":"exact","accepts_all":[{"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","extra":{"name":"USD Coin","version":"2"},"payTo":"0xD34411a70EffbDd000c529bbF572082ffDcF1794","amount":"50000","scheme":"exact","network":"eip155:8453","maxTimeoutSeconds":300},{"asset":"EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v","extra":{"feePayer":"8wLKe8H59eni5DmERU27GiRHGnN9fogRoq9yNqyKKNJA"},"payTo":"4HVvnhyXTkMnPbMBo9r3kfvYhzW4JSbLGdXg9SkUcVSe","amount":"50000","scheme":"exact","network":"solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp","maxTimeoutSeconds":300},{"asset":"0x85889c8c714505E0c94b30fcfcF64fE3Ac8FCb20","extra":{"name":"USD Coin","version":"1"},"payTo":"0xD34411a70EffbDd000c529bbF572082ffDcF1794","amount":"50000","scheme":"exact","network":"eip155:1187947933","maxTimeoutSeconds":300},{"asset":"USDC","extra":{"symbol":"USDC","nodeUrl":"https://api.keeta.com","decimals":6,"serverAddress":"keeta_aabwgiqyij4scwktdoczzvhpi33btieeses5sezeqzqmpi5ik76ttyegwuvfsai","permissionSetupUrl":"/api/v1/keeta/setup-permission"},"payTo":"keeta_aabaolle2k3hceayy4vkyw7smgl35o5wbqeebt2fibyx5sxxodneqb2rmwqkjci","amount":"50000","scheme":"keeta-usdc","network":"keeta:main","expiresAt":1771370264672,"paymentId":"3e0496ed-02cb-4568-8386-ab71bd046200","amountHuman":"0.050000","description":"Token swap via 0x Permit2. You sign EIP-712 data, append signature to tx, and broadcast. Response includes step-by-step instructions with code examples.","tokenAddress":"keeta_amnkge74xitii5dsobstldatv3irmyimujfjotftx7plaaaseam4bntb7wnna","maxTimeoutSeconds":300,"requiresPermission":true}],"asset_contract":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","max_timeout_seconds":300},"createdAt":"2026-04-21T18:32:33.446Z"}],"sources":[{"listingId":"d5b8fa57-5ca5-4f93-a32c-e4a545d81d34","source":"x402_bazaar","sourceId":"https://silverback-x402.onrender.com/api/v1/swap","sourceUrl":"https://api.cdp.coinbase.com/platform/v2/x402/discovery/resources","isPrimary":true,"firstSeenAt":"2026-04-21T18:32:33.446Z","lastSeenAt":"2026-04-22T04:02:48.273Z"}],"details":{"listingId":"d5b8fa57-5ca5-4f93-a32c-e4a545d81d34","quickStartSnippet":"curl -X POST https://silverback-x402.onrender.com/api/v1/swap \\\n  -H \"Content-Type: application/json\" \\\n  -d '{\n    \"walletAddress\": \"0xYourWalletAddress\",\n    \"tokenIn\": \"USDC\",\n    \"tokenOut\": \"WETH\",\n    \"amountIn\": \"100\",\n    \"slippage\": \"1\"\n  }'","exampleRequest":{"tokenIn":"USDC","amountIn":"100","slippage":"1","tokenOut":"WETH","walletAddress":"0x1234567890abcdef1234567890abcdef12345678"},"exampleResponse":null,"schema":null,"openapiUrl":null,"agentsTxtUrl":null,"citations":[{"claim":"The swap endpoint is priced at $0.05 per call","source_url":"https://silverback-x402.onrender.com"},{"claim":"Non-custodial token swap on Base returning EIP-712 Permit2 signing data","source_url":"https://silverback-x402.onrender.com"},{"claim":"11 pay-per-use endpoints via x402 micropayments, USDC on Base, Solana, and SKALE","source_url":"https://silverback-x402.onrender.com"},{"claim":"15% discount available when paying with $BACK token via Permit2 on Base","source_url":"https://silverback-x402.onrender.com"},{"claim":"Endpoint returns 402 Payment Required on unauthenticated POST","source_url":"https://silverback-x402.onrender.com"}],"useCases":["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"],"bestFor":["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"],"notFor":["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"],"kindDetails":{},"updatedAt":"2026-04-22T00:49:44.464Z"}}