Python: Greater choice when using `tool_choice: required`

[moonbox3]

Discussed in #5489

^{Originally posted by cecheta April 26, 2026}
Currently, when tool_choice: required is set, it gets automatically reset after the first function invocation, to prevent an infinite loop. While this makes sense, there may be times where the developer wants greater choice over the tool_choice parameter, for example leaving it set as tool_choice: required until a certain function has been called. Currently, this isn't possible without disabling automatic function calling. Is there any way such a thing could be implemented in the Agent Framework?

[cecheta]

Hi @moonbox3 , we are using FoundryChatClient.

I would think there are scenarios where someone may want to change the value of tool_choice depending on which tools have already been called. For example, keep tool_choice: required until a certain function has been called, then switch to tool_choice: none. Or, with the addition of #5309, someone could restrict the tools that are available to the agent based on which tools have already been called, while maintaining tool_choice: required. Currently, I don't think these are possible without disabling automatic function calling completely.

I'm not even sure if such a thing would be possible, however it would be nice if it was. Could a user maybe provide a function that receives the agent's last tool call, and returns the next value of tool_choice to be used in the next agent invocation? (Not sure if this would work in practice, just a suggestion).

[cecheta]

Another use case is a system where the agent has a number of functions to call - some with function implementations and others with no implementation (func=None). When the agent calls a function with an implementation, we want auto-function calling, however when the agent calls a function with no implementation, we use the function call's arguments as the agent's output, and proceed with the next step of our application. In this case, we never want the agent to produce a text output, therefore ideally we would keep tool_choice: required for all invocations.

This shouldn't cause an infinite loop, as the loop would end once one of the functions with no implementation was called.