Add max parallel_tool_calls value in Agents ModelSettings

[EnricRovira]

Please read this first

• Have you read the docs?Agents SDK docs
• => Yes
• Have you searched for related issues? Others may have had similar requests
• => yes

Describe the feature

What is the feature you're requesting? How would it work? Please provide examples and details if possible.

Currently on ModelSettings we can only choose between activating or deactivating parallel_tool_callsparam. Its a bool value.

However, there are cases where we need to restrict a maximum number of tool calls to control the context limits these tools outputs can add, and one tool call at a time is too slow.

Would be nice if we could use something like:

agent = Agent(
    name="Assistant",
    tools=[...],
    model="gpt-5",
    model_settings=ModelSettings(max_parallel_tool_calls=4),
)

Thanks!!