> ## Documentation Index > Fetch the complete documentation index at: https://docs.brdg.now/llms.txt > Use this file to discover all available pages before exploring further. # Build fast fill > Turns a fast fill quote into what the user signs. `steps` ends with one `vm: "sign"` step whose `payload` holds an EIP-712 message: sign `domain`, `types`, `primaryType` and `message` with `eth_signTypedData_v4` from the wallet in `owner`. For a token that is not USDC, `steps` can start with one `approve` to Permit2, which the wallet sends once; later fast fills of that token need only the signature. A quote from `POST /bridge/quote` is refused with `not_fast_fill`. Building the same `decisionId` again returns the same transfer. ## OpenAPI ````yaml openapi/openapi.json POST /fastfill/build openapi: 3.1.0 info: title: BRDG API version: 1.0.0 description: >- Quote, build, submit and track cross-chain transfers across every venue BRDG aggregates. servers: - url: https://api.brdg.now/v1 security: [] paths: /fastfill/build: post: tags: - fastfill summary: Build fast fill description: >- Turns a fast fill quote into what the user signs. `steps` ends with one `vm: "sign"` step whose `payload` holds an EIP-712 message: sign `domain`, `types`, `primaryType` and `message` with `eth_signTypedData_v4` from the wallet in `owner`. For a token that is not USDC, `steps` can start with one `approve` to Permit2, which the wallet sends once; later fast fills of that token need only the signature. A quote from `POST /bridge/quote` is refused with `not_fast_fill`. Building the same `decisionId` again returns the same transfer. parameters: - name: X-BRDG-Api-Key in: header required: false description: >- Optional partner key for server integrators. With it, each wallet is rate limited under the partner rather than on the IP of the calling server (a call naming no wallet, per the `userIp` in the body), bounded by a partner-wide ceiling. Unknown or disabled keys are refused with 401. See [rate limits](/api-reference/rate-limits). schema: type: string requestBody: required: true content: application/json: schema: type: object properties: decisionId: type: string pattern: >- ^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$ description: The `decisionId` from the fast fill quote response. venue: type: string minLength: 1 maxLength: 40 quoteId: type: string minLength: 1 maxLength: 200 description: Build this quote instead of `best`. userIp: anyOf: - type: string format: ip - type: string format: ip atomicBatch: type: boolean description: >- Optional, `false` when omitted. Send `true` only when the wallet will submit every returned step together as ONE atomic EIP-5792 bundle (`wallet_sendCalls` with `atomicRequired`). Then a route that can carry the fee that way returns a `fee` step beside the bridge step, listed in `feeBatch`. Otherwise the build returns no `fee` step, and the fee rides the venue's own transaction or is not charged. A transfer from Tron never carries a `fee` step. required: - decisionId example: decisionId: 5c7e4e05-1d2a-4f0b-9c3e-7a1b2c3d4e5f responses: '200': description: The transfer id and its signature step content: application/json: schema: type: object properties: transferId: type: string venue: type: string steps: type: array items: oneOf: - type: object properties: vm: type: string enum: - evm step: type: string enum: - approve - fee - main - redeem chainId: type: integer to: type: string data: type: string value: type: string gasLimit: type: string required: - vm - step - chainId - to - data - value - type: object properties: vm: type: string enum: - svm step: type: string enum: - approve - fee - main - redeem serializedTx: type: string encoding: type: string enum: - base64 - hex version: type: string enum: - v0 - legacy setPriorityFee: type: boolean refreshBlockhash: type: boolean required: - vm - step - serializedTx - encoding - version - setPriorityFee - refreshBlockhash - type: object properties: vm: type: string enum: - deposit-address step: type: string enum: - approve - fee - main - redeem venueChainId: type: string address: type: string memo: type: string tokenAddress: type: string nullable: true exactAmountAtomic: type: string expiresAt: type: integer required: - vm - step - venueChainId - address - tokenAddress - exactAmountAtomic - expiresAt - type: object properties: vm: type: string enum: - sign step: type: string enum: - approve - fee - main - redeem scheme: type: string enum: - eip712 - eip191 - ed25519 - nep413 payload: nullable: true required: - vm - step - scheme - type: object properties: vm: type: string enum: - utxo step: type: string enum: - approve - fee - main - redeem outputs: type: array items: type: object properties: address: type: string valueSats: type: string required: - address - valueSats memo: type: string feeRateSatsPerVbyte: type: number required: - vm - step - outputs - oneOf: - type: object properties: vm: type: string enum: - tron step: type: string enum: - approve - fee - main - redeem kind: type: string enum: - call contract: type: string data: type: string callValueSun: type: string feeLimitSun: type: string nullable: true required: - vm - step - kind - contract - data - callValueSun - feeLimitSun - type: object properties: vm: type: string enum: - tron step: type: string enum: - approve - fee - main - redeem kind: type: string enum: - transfer toAddress: type: string amountSun: type: string required: - vm - step - kind - toAddress - amountSun - type: object properties: vm: type: string enum: - tron step: type: string enum: - approve - fee - main - redeem kind: type: string enum: - built raw: nullable: true required: - vm - step - kind - type: object properties: vm: type: string enum: - unsupported step: type: string enum: - main reason: type: string required: - vm - step - reason deposit: type: object properties: address: type: string amountAtomic: type: string memo: type: string deadlineMs: type: integer tokenAddress: type: string nullable: true chainKey: type: string required: - address - amountAtomic - deadlineMs - tokenAddress - chainKey expiresAt: type: integer amountInAtomic: type: string expectedOutAtomic: type: string minOutAtomic: type: string feeCapture: type: string enum: - venue-param - merged - separate-step - batch - none referralCapture: type: string nullable: true enum: - merged - batch - none - null feeBasis: type: string enum: - carved - added feeBatch: type: object properties: chainId: type: integer stepIndexes: type: array items: type: integer required: - chainId - stepIndexes permit: type: object nullable: true properties: kind: type: string enum: - hypercore_deposit owner: type: string spender: type: string valueAtomic: type: string nonce: type: string deadline: type: string typedData: type: object properties: domain: type: object properties: name: type: string version: type: string chainId: type: integer verifyingContract: type: string required: - name - version - chainId - verifyingContract types: type: object additionalProperties: type: array items: type: object properties: name: type: string type: type: string required: - name - type primaryType: type: string enum: - Permit message: type: object properties: owner: type: string spender: type: string value: type: string nonce: type: string deadline: type: string required: - owner - spender - value - nonce - deadline required: - domain - types - primaryType - message default: null required: - kind - owner - spender - valueAtomic - nonce - deadline - typedData relayFeePermit: type: object nullable: true properties: kind: type: string enum: - hypercore_relay_fee owner: type: string spender: type: string valueAtomic: type: string nonce: type: string deadline: type: string typedData: type: object properties: domain: type: object properties: name: type: string version: type: string chainId: type: integer verifyingContract: type: string required: - name - version - chainId - verifyingContract types: type: object additionalProperties: type: array items: type: object properties: name: type: string type: type: string required: - name - type primaryType: type: string enum: - Permit message: type: object properties: owner: type: string spender: type: string value: type: string nonce: type: string deadline: type: string required: - owner - spender - value - nonce - deadline required: - domain - types - primaryType - message default: null required: - kind - owner - spender - valueAtomic - nonce - deadline - typedData spotTransfer: type: object nullable: true properties: kind: type: string enum: - hypercore_spot_transfer account: type: string amount: type: string nonce: type: integer signatureChainId: type: string typedData: type: object properties: domain: type: object properties: name: type: string version: type: string chainId: type: integer verifyingContract: type: string required: - name - version - chainId - verifyingContract types: type: object additionalProperties: type: array items: type: object properties: name: type: string type: type: string required: - name - type primaryType: type: string enum: - HyperliquidTransaction:UsdClassTransfer message: type: object properties: hyperliquidChain: type: string enum: - Mainnet amount: type: string toPerp: type: boolean nonce: type: integer required: - hyperliquidChain - amount - toPerp - nonce required: - domain - types - primaryType - message default: null required: - kind - account - amount - nonce - signatureChainId - typedData requoted: type: boolean requote: type: object properties: basis: type: string enum: - netOutAtomic - amountOutAtomic - amountInAtomic originalAmount: type: string freshAmount: type: string driftBps: type: integer required: - basis - originalAmount - freshAmount - driftBps boardDrift: type: object properties: corridorKey: type: string boardAmountOutAtomic: type: string firmAmountOutAtomic: type: string driftBps: type: integer boardAgeMs: type: integer required: - corridorKey - boardAmountOutAtomic - firmAmountOutAtomic - driftBps - boardAgeMs required: - transferId - venue - steps - expiresAt - amountInAtomic - expectedOutAtomic - minOutAtomic - feeCapture - referralCapture - feeBasis - requoted example: transferId: 6f1d2c0a-4b7e-4c55-9a1e-2f0e8c3b7d41 venue: relay steps: - vm: sign step: main scheme: eip712 payload: owner: '0x58E602386DB134b1F9B1d6d390C11A2B7b486677' domain: name: USD Coin version: '2' chainId: 8453 verifyingContract: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913' types: ReceiveWithAuthorization: - name: from type: address - name: to type: address - name: value type: uint256 - name: validAfter type: uint256 - name: validBefore type: uint256 - name: nonce type: bytes32 primaryType: ReceiveWithAuthorization message: from: '0x58E602386DB134b1F9B1d6d390C11A2B7b486677' to: '0xccc88a9d1b4ed6b0eaba998850414b24f1c315be' value: '10000000' validAfter: 0 validBefore: 1791484288 nonce: >- 0x8ee9dabf3ef81e81899d9c395fa7d681a7435a88d0deb19916b7b9db027a8f53 venueSubmit: endpoint: /execute/permits body: kind: eip3009 requestId: >- 0x17914836885153788c87ec28425d97ef85bd8916e6bb58e8a52d45c0fd169cd6 api: swap expiresAt: 1791483388000 amountInAtomic: '10000000' expectedOutAtomic: '9968392' minOutAtomic: '9769024' requoted: false feeCapture: venue-param referralCapture: null feeBasis: carved '400': description: >- Malformed request, an unknown asset, or a signed transaction that is not what we built content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: nullable: true retryAfterMs: type: integer required: - code - message required: - error '401': description: >- An `X-BRDG-Api-Key` header was sent and the key is unknown (`invalid_api_key`) or disabled (`api_key_disabled`) content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: nullable: true retryAfterMs: type: integer required: - code - message required: - error '404': description: No such decision or transfer, or the aggregator is switched off content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: nullable: true retryAfterMs: type: integer required: - code - message required: - error '409': description: >- The decision is indicative, the quote expired or drifted, the venue is ineligible, or execution is switched off content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: nullable: true retryAfterMs: type: integer required: - code - message required: - error '429': description: Rate limited; retry after `retryAfterMs` content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: nullable: true retryAfterMs: type: integer required: - code - message required: - error '502': description: The venue refused to build, or the broadcast was rejected content: application/json: schema: type: object properties: error: type: object properties: code: type: string message: type: string details: type: object additionalProperties: nullable: true retryAfterMs: type: integer required: - code - message required: - error ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.