Support pydantic `Field` annotations in tool arguments

[georg-wolflein]

Currently, the @function_tool decorator does not support the pydantic Field annotation to constrain the values of the function arguments, e.g. to be an integer within a certain range.

Example

Consider the example below:

import json

from pydantic import Field

from agents import function_tool


@function_tool
def my_tool(age: int = Field(..., gt=0)) -> str:
    return f"The age is {age}"


print(json.dumps(my_tool.params_json_schema, indent=2))

Output:

{
  "properties": {
    "age": {
      "title": "Age",
      "type": "integer"
    }
  },
  "title": "my_tool_args",
  "type": "object",
  "additionalProperties": false,
  "required": [
    "age"
  ]
}

The constraint that the age should be greater than 0 is not part of the JSON schema.

Workaround

It is currently possible to get such constraints in nested BaseModels. However, I don't think that putting the actual function arguments in a nested BaseModel is an ideal solution.

import json

from pydantic import BaseModel, Field

from agents import function_tool


class MyToolInput(BaseModel):
    age: int = Field(..., gt=0)


@function_tool
def my_tool(input: MyToolInput) -> str:
    return f"The age is {input.age}"


print(json.dumps(my_tool.params_json_schema, indent=2))

Output:

{
  "$defs": {
    "MyToolInput": {
      "properties": {
        "age": {
          "exclusiveMinimum": 0,
          "title": "Age",
          "type": "integer"
        }
      },
      "required": [
        "age"
      ],
      "title": "MyToolInput",
      "type": "object",
      "additionalProperties": false
    }
  },
  "properties": {
    "input": {
      "$ref": "#/$defs/MyToolInput"
    }
  },
  "required": [
    "input"
  ],
  "title": "my_tool_args",
  "type": "object",
  "additionalProperties": false
}

In the workaround, the age has an exclusiveMinimum. My feature request is that the exclusiveMinimum would also be present in the original example above.

I will submit a PR to implement this functionality shortly.