Description

The strands tool decorator is removing "$defs" from the generated tool spec, which leads to validation errors or poor quality responses. Take for example the following tool:

class TimeSpec(pydantic.BaseModel):
    """City name and timezone."""

    city: str = pydantic.Field(description="City name, e.g., New York.")
    timezone: str = pydantic.Field(description="Time zone, e.g., EST.")


@strands.tool
def current_time(spec: TimeSpec) -> str:
    return ...

The resulting tool spec is:

{
  "name": "current_time",
  "description": "current_time",
  "input_schema": {
    "properties": {
      "spec": {
        "$ref": "#/$defs/TimeSpec",
        "description": "Parameter spec"
      }
    },
    "required": [
      "spec"
    ],
    "type": "object"
  }
}

Notice however that the "$ref" remains. I tested this on a few model providers. If I run through bedrock, I encounter the following error:

botocore.errorfactory.ValidationException: An error occurred (ValidationException) when calling the ConverseStream operation: The model returned the following errors: tools.0.custom.input_schema: JSON schema is invalid. It must match JSON Schema draft 2020-12 (https://json-schema.org/draft/2020-12). Learn more about tool use at https://docs.anthropic.com/en/docs/tool-use.

If I run this through openai, I do not receive a validation error but instead a poor quality response:

I'm sorry, I can't provide the current time right now. However, you can quickly find the current time in New York by doing a quick web search or by checking the world clock function of your device.

This PR removes the filtering of "$defs". My example tool schema then looks as follows:

{
  "name": "current_time",
  "description": "current_time",
  "input_schema": {
    "$defs": {
      "TimeSpec": {
        "description": "City name and timezone.",
        "properties": {
          "city": {
            "description": "City name, e.g., New York.",
            "title": "City",
            "type": "string"
          },
          "timezone": {
            "description": "Time zone, e.g., EST.",
            "title": "Timezone",
            "type": "string"
          }
        },
        "required": [
          "city",
          "timezone"
        ],
        "title": "TimeSpec",
        "type": "object"
      }
    },
    "properties": {
      "spec": {
        "$ref": "#/$defs/TimeSpec",
        "description": "Parameter spec"
      }
    },
    "required": [
      "spec"
    ],
    "type": "object"
  }
}

Related Issues

#247

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Testing

• I ran hatch run prepare
• I also directly invoked each model provider (minus LlamaAPIModel) with my sample tool included in the spec. All successfully called the tool.
  • I don't have a LlamaAPIModel key which is why this one was excluded. However, I did test the llama3.3 model through the OllamaModel provider.

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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