[Winoren (Winoren)]

Why are these changes needed?

HttpTool accepts JSON Schema string formats such as date, date-time, and uuid. The generated input model validates those strings into Python date, datetime, and UUID instances. run() currently exports them with model_dump() in Python mode and passes the resulting objects to HTTPX's JSON encoder. Valid tool arguments consequently raise TypeError: Object of type ... is not JSON serializable before any HTTP request is sent.

Export arguments in Pydantic's JSON mode so validated formats become JSON-compatible values. Path parameters are still removed from the body, and ordinary boolean/integer values retain their JSON types.

Nine regression cases cover all three formats with POST, PUT, and PATCH through the real HttpTool.run_json() and HTTPX request encoding. Only the transport is replaced with MockTransport; no external service is called by these cases.

Related issue number

Found while inspecting the current HTTP tool implementation; no linked issue. This is separate from the existing configuration round-trip and path-escaping fixes.

Validation

Based on upstream 027ecf0a379bcc1d09956d46d12d44a3ad9cee14, using an isolated Python 3.11 environment installed with uv (editable core/ext/test-utils, HTTP tool dependencies, and local test server dependencies):

• Before the fix: all 9 new cases fail with JSON serialization errors for date, datetime, or UUID.
• python -m pytest python/packages/autogen-ext/tests/tools/http/test_http_tool.py -k 'not invalid_request' -q: 23 passed, 1 deselected after the fix.
• Full HTTP test file: 23 passed, 1 failed. Existing test_invalid_request expects host fake to raise a connection error, but it receives a response in this environment. Restoring the upstream implementation and running that test alone reproduces the same failure. Removing proxy environment variables also did not resolve it; no change to that test is included here.
• Ruff 0.4.8 lint and format checks on both changed files: passed.
• Mypy 1.13.0, --config-file python/pyproject.toml --follow-imports=silent on both changed files: passed.
• git diff --check: passed.

Full workspace checks and documentation builds were not run.

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. No documentation change is needed for this serialization correction.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed. Local results and the baseline failure are documented above; upstream checks are pending.

Prepared with Codex assistance.