> ## Documentation Index > Fetch the complete documentation index at: https://docs.kalshi.com/llms.txt > Use this file to discover all available pages before exploring further. # Propose Block Trade > Endpoint for creating a block trade proposal. ## OpenAPI ````yaml /openapi.yaml post /communications/block-trade-proposals openapi: 3.0.0 info: title: Kalshi Trade API Manual Endpoints version: 3.26.0 description: >- Manually defined OpenAPI spec for endpoints being migrated to spec-first approach servers: - url: https://external-api.kalshi.com/trade-api/v2 description: Production Trade API server - url: https://api.elections.kalshi.com/trade-api/v2 description: Production shared API server, also supported - url: https://external-api.demo.kalshi.co/trade-api/v2 description: Demo Trade API server - url: https://demo-api.kalshi.co/trade-api/v2 description: Demo shared API server, also supported security: [] tags: - name: api-keys description: API key management endpoints - name: orders description: Order management endpoints - name: order-groups description: Order group management endpoints - name: portfolio description: Portfolio and balance information endpoints - name: communications description: Request-for-quote (RFQ) endpoints - name: multivariate description: Multivariate event collection endpoints - name: exchange description: Exchange status and information endpoints - name: live-data description: Live data endpoints - name: markets description: Market data endpoints - name: milestone description: Milestone endpoints - name: search description: Search and filtering endpoints - name: incentive-programs description: Incentive program endpoints - name: fcm description: FCM member specific endpoints - name: events description: Event endpoints - name: structured-targets description: Structured targets endpoints paths: /communications/block-trade-proposals: post: tags: - communications summary: Propose Block Trade description: ' Endpoint for creating a block trade proposal.' operationId: ProposeBlockTrade requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/ProposeBlockTradeRequest' responses: '201': description: Block trade proposal created successfully content: application/json: schema: $ref: '#/components/schemas/ProposeBlockTradeResponse' '400': $ref: '#/components/responses/BadRequestError' '401': $ref: '#/components/responses/UnauthorizedError' '403': $ref: '#/components/responses/ForbiddenError' '500': $ref: '#/components/responses/InternalServerError' security: - kalshiAccessKey: [] kalshiAccessSignature: [] kalshiAccessTimestamp: [] components: schemas: ProposeBlockTradeRequest: type: object required: - buyer_user_id - seller_user_id - market_ticker - price_centi_cents - centicount - maker_side - expiration_ts properties: buyer_user_id: type: string description: User ID of the buyer x-oapi-codegen-extra-tags: validate: required buyer_subtrader_id: type: string description: >- Subtrader ID of the buyer. Provide either this or buyer_subaccount, not both. x-go-type-skip-optional-pointer: true buyer_subaccount: type: integer minimum: 0 maximum: 63 description: >- User-managed subaccount number of the buyer (0 for primary, 1-63 for numbered subaccounts). Provide either this or buyer_subtrader_id, not both. seller_user_id: type: string description: User ID of the seller x-oapi-codegen-extra-tags: validate: required seller_subtrader_id: type: string description: >- Subtrader ID of the seller. Provide either this or seller_subaccount, not both. x-go-type-skip-optional-pointer: true seller_subaccount: type: integer minimum: 0 maximum: 63 description: >- User-managed subaccount number of the seller (0 for primary, 1-63 for numbered subaccounts). Provide either this or seller_subtrader_id, not both. market_ticker: type: string description: The ticker of the market for this block trade x-oapi-codegen-extra-tags: validate: required price_centi_cents: type: integer format: int64 minimum: 1 description: Price in centi-cents x-oapi-codegen-extra-tags: validate: required,gt=0 centicount: type: integer format: int64 minimum: 1 description: Number of contracts in centicounts x-oapi-codegen-extra-tags: validate: required,gt=0 maker_side: type: string description: The maker side of the trade enum: - 'yes' - 'no' x-oapi-codegen-extra-tags: validate: required,oneof=yes no expiration_ts: type: string format: date-time description: Expiration time of the proposal x-oapi-codegen-extra-tags: validate: required ProposeBlockTradeResponse: type: object required: - block_trade_proposal_id properties: block_trade_proposal_id: type: string description: The ID of the newly created block trade proposal ErrorResponse: type: object properties: code: type: string description: Error code message: type: string description: Human-readable error message details: type: string description: Additional details about the error, if available service: type: string description: The name of the service that generated the error responses: BadRequestError: description: Bad request - invalid input content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' UnauthorizedError: description: Unauthorized - authentication required content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' ForbiddenError: description: Forbidden - insufficient permissions content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' InternalServerError: description: Internal server error content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' securitySchemes: kalshiAccessKey: type: apiKey in: header name: KALSHI-ACCESS-KEY description: Your API key ID kalshiAccessSignature: type: apiKey in: header name: KALSHI-ACCESS-SIGNATURE description: RSA-PSS signature of the request kalshiAccessTimestamp: type: apiKey in: header name: KALSHI-ACCESS-TIMESTAMP description: Request timestamp in milliseconds ````