What changes?
Responses API combines conversation and tool use in one interface. A business workflow can move from understanding a question to retrieving information and proposing an action. Your application still defines which operations are available and who may run them.
Example: order tracking
Start with an order-status tool that verifies ownership and returns only the status and update time. Let the model explain those fields. Address changes need a separate action with a preview and confirmation. Never include other customers’ records in the conversation context.
Measure the outcome
Test missing orders, ownership failures and a slow order service. A correct answer or clear failure is preferable to an invented status. Track completed-task cost, latency and human handoffs before adding more actions.