# Unexpected additionalProperties requirement for nested Pydantic models in response\_format

**URL:** <https://community.openai.com/t/unexpected-additionalproperties-requirement-for-nested-pydantic-models-in-response-format/1151727>\
**Category:** API\
**Created:** [March 25, 2025, 1:36pm UTC](https://community.openai.com/t/unexpected-additionalproperties-requirement-for-nested-pydantic-models-in-response-format/1151727 "2025-03-25T13:36:27Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![oran.sh](https://sea2.discourse-cdn.com/openai1/user_avatar/community.openai.com/oran.sh/32/448694_2.png) [@oran.sh](https://community.openai.com/u/oran.sh)\
**Post date:** [March 25, 2025, 1:36pm UTC](https://community.openai.com/t/unexpected-additionalproperties-requirement-for-nested-pydantic-models-in-response-format/1151727/1 "2025-03-25T13:36:27Z")

</div>

I’m encountering an error when using the following Pydantic model as response\_schema in the API. The error only occurs with specific nested models, but not others that appear to have a similar structure.

Here’s the model:

```auto
from enum import Enum
from typing import List, Optional
from pydantic import BaseModel, Field

class ElementCategory(str, Enum):
    visual = "visual"
    audio = "audio"

class DetailLevel(str, Enum):
    minimal = "minimal"
    moderate = "moderate"

class ModelApproach(BaseModel):
    overall_style: str = Field(...)
    distinctive_features: List[str] = Field(...)

class SceneMapping(BaseModel):
    v1_scenes: List[str] = Field(...)
    v2_scenes: List[str] = Field(...)

class HighLevelComparison(BaseModel):
    v1_approach: ModelApproach = Field(...)
    v2_approach: ModelApproach = Field(...)
    scene_mapping: SceneMapping = Field(...)

class ElementComparison(BaseModel):
    element_name: str = Field(...)
    element_category: ElementCategory = Field(...)
    difference_notes: str = Field(...)

class SceneComparison(BaseModel):
    scene_id: str = Field(...)
    elements_comparison: List[ElementComparison] = Field(...)
    elements_unique_to_v1: List[str] = Field(...)

class ModelComparisonResponse(BaseModel):
    high_level_comparison: HighLevelComparison = Field(...)
    scene_comparisons: List[SceneComparison] = Field(...)
    conclusion: List[str] = Field(...)

```

And here is the call:

```auto
      PROMPT_MESSAGES = [
          {"role": "system", "content": self.system},
          {
              "role": "user",
              "content": [
                  {
                      "type": "text",
                      "text": prompt
                  }
              ]
          }
      ]

        params = {
            "model": 'o3-mini',
            "messages": PROMPT_MESSAGES,
            "max_completion_tokens": 10000,
            "seed": 33,
        }

        result = self.beta.chat.completions.parse(
            **params,
            response_format=ModelComparisonResponse
        )
        return result.choices[0].message.content

```

I am getting this error:

```auto
Error code: 400 - {'error': {'message': "Invalid schema for response_format 'ModelComparisonResponse': In context=('properties', 'v1_approach'), 'additionalProperties' is required to be supplied and to be false.", 'type': 'invalid_request_error', 'param': 'response_format', 'code': None}}

```

Interestingly:

1. When I add model\_config = {“json\_schema\_extra”: {“additionalProperties”: False}} to the ModelApproach class, I still get errors.
2. When I add the same config to both ModelApproach and SceneMapping, it seems to work.
3. When I comment out high\_level\_comparison from ModelComparisonResponse, everything works fine despite scene\_comparisons containing equally nested models.

This seems inconsistent since the SceneComparison model also has nested models (ElementComparison), yet only the models under HighLevelComparison trigger the error.

Anyone able to understand why I got this error only for some of the nested models? Thanks!

---

<div class="post-metadata">

**Author:** ![\_j](https://sea2.discourse-cdn.com/openai1/user_avatar/community.openai.com/_j/32/766292_2.png) [@\_j](https://community.openai.com/u/_j)\
**Post date:** [March 25, 2025, 2:26pm UTC](https://community.openai.com/t/unexpected-additionalproperties-requirement-for-nested-pydantic-models-in-response-format/1151727/2 "2025-03-25T14:26:30Z")

</div>

You can do what the SDK schema maker seems not to be doing - putting in the expected additionalProperties at all nest levels that are required.

```python
class ElementCategory(str, Enum):
    visual = "visual"
    audio = "audio"

class DetailLevel(str, Enum):
    minimal = "minimal"
    moderate = "moderate"

class ModelApproach(BaseModel):
    overall_style: str = Field(...)
    distinctive_features: List[str] = Field(...)
    
    model_config = ConfigDict(extra='forbid')

class SceneMapping(BaseModel):
    v1_scenes: List[str] = Field(...)
    v2_scenes: List[str] = Field(...)

    model_config = ConfigDict(extra='forbid')

class HighLevelComparison(BaseModel):
    v1_approach: ModelApproach = Field(...)
    v2_approach: ModelApproach = Field(...)
    scene_mapping: SceneMapping = Field(...)

    model_config = ConfigDict(extra='forbid')

class ElementComparison(BaseModel):
    element_name: str = Field(...)
    element_category: ElementCategory = Field(...)
    difference_notes: str = Field(...)

    model_config = ConfigDict(extra='forbid')

class SceneComparison(BaseModel):
    scene_id: str = Field(...)
    elements_comparison: List[ElementComparison] = Field(...)
    elements_unique_to_v1: List[str] = Field(...)

    model_config = ConfigDict(extra='forbid')

class ModelComparisonResponse(BaseModel):
    high_level_comparison: HighLevelComparison = Field(...)
    scene_comparisons: List[SceneComparison] = Field(...)
    conclusion: List[str] = Field(...)

    model_config = ConfigDict(extra='forbid')

```

Which was satisfied by responses.parse()

The curious person could see exactly which level is not having this requirement done for you, to then open up a github openai library issue.

---

<div class="post-metadata">

**Author:** ![oran.sh](https://sea2.discourse-cdn.com/openai1/user_avatar/community.openai.com/oran.sh/32/448694_2.png) [@oran.sh](https://community.openai.com/u/oran.sh)\
**Post date:** [March 25, 2025, 8:16pm UTC](https://community.openai.com/t/unexpected-additionalproperties-requirement-for-nested-pydantic-models-in-response-format/1151727/3 "2025-03-25T20:16:09Z")

</div>

ok this seems to be solved in v1.68.2 of the python SDK…  
I wasn’t aligned to newest version. Sorry about that