Extra config required for with_structured_output with Provisioned Throughput

[athewsey]

(Sorry there's not as much detail here as I'd like, but it's a second-hand report from ~3 weeks ago, from a customer we've been working with - and I haven't yet been able to get my hands on a PT deployment to fully reproduce, get stack traces, etc)

Symptom: ChatBedrockConverse.with_structured_output fails when using Claude (3) on Provisioned Throughput, but works with On-Demand

Cause:

• ChatBedrock and ChatBedrockConverse both use model_id-based logic to determine default values for supports_tool_choice_values.
• When using a Provisioned Throughput endpoint, this logic fails because the PT ARN (passed as model_id) is opaque as to what model is deployed.
• With the inferred supports_tool_choice_values = () value, with_structured_output fails to parse the response into the provided data model.

Workaround: Explicitly specify supports_tool_choice_value = ["auto", "any", "tool"] in the constructor

Asks:

1. Would it be feasible for LangChain to:
   • Detect when the passed model_id is a PT ARN
   • Attempt to look up the underlying model ID via e.g. the GetProvisionedModelThroughput API, and use that for the tool choice (and whatever else needs model ID) if possible
   • (I guess log a warning in case the model ID couldn't be automatically looked-up, due to e.g. not having IAM permission for that separate API call)
2. It seems unexpected that this feature would fail if tools aren't available - shouldn't it default to client-side orchestration? It'd be great if we could check exactly what the expected behaviour here is and maybe expand the documentation?

[3coins]

@athewsey
A current workaround for this is to pass the provider value when initiating the class. This should pick the right set of settings for the anthropic models when used with the ChatBedrockConverse class. We are tracking fix for this in #253, which will include some of the suggestions you mentioned.