[nknj]

one additional difference between chat and responses is the number model turns a single api call can make. chat completions is a single turn api primitive -- which means it can talk to the model just once. responses is capable of making multiple model turns and tool calls in a single api call.

for example, you can give the responses api access to 3 tools: a vector store with some user memories (file_search), the shopify mcp server, and code_interpreter. you can then ask it to look up some user memories, find relevant items in the shopify mcp store, and then download them into a csv file. all of this can be done in a single api call that involves multiple model turns and tool calls.

p.s. - you can also use responses statelessly by setting store=false.

[OutOfHere]

What are my choices for using a custom tool? Does it come down to: function calling (single turn), MCP (multi-turn via Responses)? What else are my choices?

Why would anyone want to use Responses statelessly? Just trying to understand.

[swyx]

i think the original intent of responses api was also to unify the realtime experiences into responses - is that accurate?

[nknj]

we expect responses and realtime to be our 2 core api primitives long term — responses for turn by turn interactions and realtime for models requiring low latency bidirectional streams to/from the apps/models.