[Microsoft Extensions] Strict is being populated for even `structured-outputs-2025-11-13`

[PederHP]

anthropic-sdk-csharp/src/Anthropic/Services/Beta/Messages/AnthropicBetaClientExtensions.cs

Line 949 in 957b674

Strict = GetValue<bool?>(af, nameof(BetaTool.Strict)),

When passing any tool to a beta client, even if structured-outputs-2025-11-13 is not set, the Strict tool is sent (presumably with a default). This isn't allowed if the beta header isn't present and results in the following API error:
tools 0 custom strict extra inputs are not permitted

Either the presence of the property should auto-include the header, or the property should only be included if the header is set via RawRepresentationFactory.

NB! This might be an issue even without using IChatClient extensions - I haven't verified this yet. But the API definitely doesn't want that property being sent if the beta headers is not set.

[TomerAberbach]

cc @stephentoub

[stephentoub]

Strict special-cases null to make it a nop:

anthropic-sdk-csharp/src/Anthropic/Models/Beta/Messages/BetaTool.cs

Lines 224 to 227 in 957b674

	if (value == null)
	{
	return;
	}

and GetValue should be returning null if you haven't set that value in AdditionalProperties:

anthropic-sdk-csharp/src/Anthropic/Services/Beta/Messages/AnthropicBetaClientExtensions.cs

Line 964 in 957b674

: default;

@PederHP, are you seeing otherwise? I'm missing how this GetValue call would be problematic.

[PederHP]

I'll create a repro. I just saw the tools.0.custom.strict extra inputs are not permitted error bubble up. Maybe it's being sent as null (ie not explicitly excluded from the serialization) and the API is complaining about that?