fix(agent_tool_input): summarize Pydantic Optional[T] anyOf fields

[adityasingh2400]

Summary

• The schema summary helper rejected any field with an anyOf key, but Pydantic renders T | None as anyOf: [{type: T}, {type: "null"}]. Because _summarize_json_schema returns None for the whole schema when any single field is unsupported, one Optional[T] field would silently suppress the entire structured-input summary, including sibling fields with valid types and descriptions.
• Detect the 2-branch anyOf of a simple type plus null and render it as T | null, matching the existing type: ["T", "null"] path.
• Other anyOf shapes (unions of two non-null types, anyOf with nested objects, etc.) are still rejected.

Repro

from pydantic import BaseModel, TypeAdapter
from agents.agent_tool_input import build_structured_input_schema_info

class Args(BaseModel):
    count: int | None = None  # Pydantic emits anyOf: [{type:integer},{type:null}]
    name: str  # has a description in the rendered schema

schema = TypeAdapter(Args).json_schema()
# add descriptions for the demo
schema["properties"]["count"]["description"] = "Optional count."
schema["properties"]["name"]["description"] = "A name."

print(build_structured_input_schema_info(schema, include_json_schema=False).summary)
# Before: None  (entire summary dropped)
# After:
#   - count (integer | null, optional) - Optional count.
#   - name (string, required) - A name.

Test plan

• New test test_schema_summary_handles_pydantic_optional_anyof covers the nullable anyOf shape and confirms non-nullable anyOf unions are still rejected.
• Test fails on main (assert None is not None) and passes with the fix.
• All existing tests/test_agent_tool_input.py, tests/test_agent_tool_state.py, and tests/test_agent_as_tool.py tests still pass (60/60).

[seratch]

@codex review

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve enum/const constraints in nullable anyOf

Pydantic emits Optional[Literal[...]] as anyOf with an enum/const branch that also has type: "string". This helper now accepts that branch as a bare simple type, so the schema summary says e.g. string | null instead of the allowed literals, misleading the nested agent about valid structured input.

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