Have any free model provider that can be used for structure output? (output_type argument when creating an agent)?

[phuccodetrau]

@DataClass
class EvaluationFeedback:
feedback: str
score: Literal["pass", "needs_improvement", "fail"]

evaluator = Agent[None](
name="evaluator",
model="deepseek/deepseek-chat-v3-0324:free",
instructions=(
"You evaluate a story outline and decide if it's good enough."
"If it's not good enough, you provide feedback on what needs to be improved."
"Never give it a pass on the first try."
),
output_type=EvaluationFeedback,
)

I have used api from Openrouter for the deepseek model like above but it seems that it can't cast the model output to the predefined Evaluation Feedback

agents.exceptions.ModelBehaviorError: Invalid JSON when parsing I can refine it further! for TypeAdapter(OutputType); 1 validation error for typed-dict
Invalid JSON: expected ident at line 1 column 3 [type=json_invalid, input_value=' I can refine it further!', input_type=str]
For further information visit https://errors.pydantic.dev/2.10/v/json_invalid

Process finished with exit code 1

[rm-openai]

It might work if you add stuff like this to the prompt:

Only output JSON. Do not output anything else. I will be parsing this with Pydantic so output valid JSON only. Follow this JSON schema:
{EvaluationFeedback.model_json_schema()}

[phuccodetrau]

thank you