Alpaca Broker API — Trading on Behalf of Accounts

Place, modify, cancel, and track orders for an end-user account, and read positions & buying power. The defining feature of Broker API trading: account_id is in the path — you act for a user account, not your own.

Read alpaca-broker-integration first. Broker API + HTTP Basic auth. (The standalone Trading API uses /v2/orders with no account in the path; everything else here transfers.)

Reference

• Guides: https://docs.alpaca.markets/docs/orders-at-alpaca, https://docs.alpaca.markets/docs/fractional-trading
• API ref: https://docs.alpaca.markets/reference/postorder
• Live schema: alpaca-docs MCP → get-endpoint title "Broker API" path /v1/trading/accounts/{account_id}/orders

1. Endpoints