[FEATURE]: Add Anthropic's Structured Output feature

[manbradcalf]

Description

Anthropic recently added structured outputs to their SDK. You can use it via API or SDK.

This feature request is simply to add structured output support for AnthropicLLM alongside OpenAILLM and VertexLLM providers.

Here is how to use Anthropic Structured Ouputs...

SDK

from pydantic import BaseModel
from anthropic import Anthropic


class ContactInfo(BaseModel):
    name: str
    email: str
    plan_interest: str
    demo_requested: bool


client = Anthropic()

response = client.messages.parse(
    model="claude-opus-4-6",
    max_tokens=1024,
    messages=[
        {
            "role": "user",
            "content": "Extract the key information from this email: John Smith (john@example.com) is interested in our Enterprise plan and wants to schedule a demo for next Tuesday at 2pm.",
        }
    ],
    output_format=ContactInfo,
)

print(response.parsed_output)

REST

curl https://api.anthropic.com/v1/messages \
  -H "content-type: application/json" \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -d '{
    "model": "claude-opus-4-6",
    "max_tokens": 1024,
    "messages": [
      {
        "role": "user",
        "content": "Extract the key information from this email: John Smith (john@example.com) is interested in our Enterprise plan and wants to schedule a demo for next Tuesday at 2pm."
      }
    ],
    "output_config": {
      "format": {
        "type": "json_schema",
        "schema": {
          "type": "object",
          "properties": {
            "name": {"type": "string"},
            "email": {"type": "string"},
            "plan_interest": {"type": "string"},
            "demo_requested": {"type": "boolean"}
          },
          "required": ["name", "email", "plan_interest", "demo_requested"],
          "additionalProperties": false
        }
      }
    }
  }'

Would be great to have Anthropic added alongside OpenAI and Vertex as a provider that supports Structured Outputs

Additional Info

[neo4j-graphrag-python Structued Output docs] (https://neo4j.com/docs/neo4j-graphrag-python/current/user_guide_kg_builder.html#using-structured-output)

Anthropic Structured Output docs