> ## Documentation Index > Fetch the complete documentation index at: https://docs.derive.xyz/llms.txt > Use this file to discover all available pages before exploring further. # private/simulate_block_trade > Estimates one side of a block trade for the caller's subaccount before it is signed. Takes the side's direction, the agreed priced legs and an optional extra_fee. Returns the total fee the side would pay, extra_fee included, its initial margin before and after the trade, and within_price_band, which is whether the total cost is inside the currency's RFQ price band for both sides, or null if the currency has no band. Fails with invalid_amount (11012) if a leg is smaller than 100 times its instrument's minimum_amount. A side without enough margin returns is_valid false and the reason, not an error. Requires the block_trade off-chain scope. ## OpenAPI ````yaml /openapi.json post /private/simulate_block_trade openapi: 3.1.0 info: title: Derive v3 API version: 0.2.0 description: JSON-RPC 2.0 methods, served over WebSocket and HTTP POST. servers: - url: https://api.derive.xyz/v3 description: Production (HTTP POST base) - url: https://testnet.api.derive.xyz/v3 description: Testnet (HTTP POST base) security: [] tags: - name: Subaccounts description: >- List, inspect, and label subaccounts, portfolios, positions, and collateral. - name: Session Keys description: Register, edit, and list delegated signing keys. - name: Account description: Wallet-level account information and settings. - name: Orderbook description: Place, replace, cancel, and query orders, trigger orders, and algos. - name: RFQ description: 'Request-for-quote: send RFQs, quote, and execute block trades.' - name: Liquidations description: >- Open a Dutch auction against a breaching subaccount, quote the auctions running right now, bid on them, and review past ones. - name: Vault Shareholders description: >- Deposit into and withdraw from vaults, and track shares, requests, and performance. - name: Vault Curators description: >- Create and operate curated vaults: settle deposit and withdrawal requests, and manage vault metadata. - name: History description: >- Per-account historical records: orders, trades, transfers, and settlements. - name: Market Maker Protection description: Configure, read, and reset market-maker protection. - name: Transfers & Withdrawals description: Move collateral between subaccounts, to other wallets, and on-chain. - name: Onchain Actions description: >- L1 onchain actions submitted via OnchainActionManager: register deposit addresses, list pending deposits, and inspect onchain action history. - name: System description: Rate limits, transaction lookups, and live incidents. - name: Market Data description: Instruments, currencies, tickers, and market-wide feeds. - name: Maker Scoring description: Maker programs, score breakdowns, and detailed scoring snapshots. - name: Referrals description: Referral codes and program performance. - name: Chat description: Anonymous chat rooms and conversations with the concierge. - name: Other description: Uncategorized. paths: /private/simulate_block_trade: post: tags: - RFQ summary: private/simulate_block_trade description: >- Estimates one side of a block trade for the caller's subaccount before it is signed. Takes the side's direction, the agreed priced legs and an optional extra_fee. Returns the total fee the side would pay, extra_fee included, its initial margin before and after the trade, and within_price_band, which is whether the total cost is inside the currency's RFQ price band for both sides, or null if the currency has no band. Fails with invalid_amount (11012) if a leg is smaller than 100 times its instrument's minimum_amount. A side without enough margin returns is_valid false and the reason, not an error. Requires the block_trade off-chain scope. operationId: private_simulate_block_trade requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SimulateBlockTradeRequest' responses: '200': description: Success content: application/json: schema: $ref: '#/components/schemas/BlockTradeSideCheckResponse' default: description: JSON-RPC error (see Error Codes) content: application/json: schema: type: object required: - error properties: error: $ref: '#/components/schemas/RPCError' security: - DeriveWallet: [] DeriveTimestamp: [] DeriveSignature: [] components: schemas: SimulateBlockTradeRequest: type: object required: - direction - legs - subaccount_id properties: direction: $ref: '#/components/schemas/Direction' description: >- This side's direction. The taker side trades opposite the maker side. extra_fee: description: Broker fee for this side, in USD. default: '0' type: string format: decimal legs: description: The agreed priced legs, the same on both sides. type: array items: $ref: '#/components/schemas/PricedLegParamsAndResponse' subaccount_id: type: integer format: int64 BlockTradeSideCheckResponse: description: >- Result for `private/simulate_block_trade` and `private/verify_block_trade`: one side's fee and margin if it executed now. type: object required: - estimated_fee - is_valid - post_initial_margin - pre_initial_margin properties: estimated_fee: description: The side's total fee, `extra_fee` included. type: string format: decimal expires_at_sec: description: >- The last second at which the signed side can execute. Null for an unsigned side. type: - integer - 'null' format: int64 invalid_reason: type: - string - 'null' is_valid: description: >- False if the side does not have enough margin for its trade and fees, or if the trade takes the subaccount over its maximum asset count. type: boolean post_initial_margin: description: >- Decimal string of the human value (e.g. `"1.5"`), up to 12 fractional digits; a string or JSON number is accepted type: string format: decimal pre_initial_margin: description: >- Decimal string of the human value (e.g. `"1.5"`), up to 12 fractional digits; a string or JSON number is accepted type: string format: decimal within_price_band: description: >- Whether both sides are within the currency's RFQ price band. Null if it has no band. type: - boolean - 'null' RPCError: type: object required: - code - message properties: code: type: integer format: int64 data: type: - string - 'null' message: type: string Direction: type: string enum: - buy - sell PricedLegParamsAndResponse: type: object required: - amount - direction - instrument_name - price properties: amount: description: >- Non-negative decimal string of the human value (e.g. `"1.5"`), up to 12 fractional digits; a string or JSON number is accepted type: string format: decimal direction: $ref: '#/components/schemas/Direction' instrument_name: type: string price: description: >- Non-negative decimal string of the human value (e.g. `"1.5"`), up to 12 fractional digits; a string or JSON number is accepted type: string format: decimal securitySchemes: DeriveWallet: type: apiKey in: header name: X-DeriveWallet description: The wallet the request acts for. DeriveTimestamp: type: apiKey in: header name: X-DeriveTimestamp description: The current time in milliseconds, as a decimal string. DeriveSignature: type: apiKey in: header name: X-DeriveSignature description: >- EIP-191 signature of the timestamp, by the wallet or one of its session keys. ```` ## Related topics - [private/execute_block_trade](https://docs.derive.xyz/api-reference/rfq/privateexecute_block_trade.md) - [RFQ Trading](https://docs.derive.xyz/trading/rfq.md) - [Changelog](https://docs.derive.xyz/changelog.md) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.