Python: [BREAKING] Remove FunctionTool[Any] compatibility shim for schema passthrough (#3600)

[eavanvalkenburg]

Summary

Fixes #3600

This PR simplifies FunctionTool schema handling so schema-based tools no longer rely on generated Pydantic models at runtime.

What changed

• Removed FunctionTool generic ArgsT usage and simplified FunctionTool typing.
• For schema-supplied tools, creation/schema/invoke now work without requiring a Pydantic model.
• invoke() accepts mapping arguments directly and performs lightweight schema checks.
• _auto_invoke_function() now validates schema-supplied tool arguments without model_validate.
• MCP prompt/tool schema handling now uses plain schema dicts (no prompt-side Pydantic model creation; tool schema passed through directly).
• Consolidated schema passthrough tests into existing core test files and removed test_schema_passthrough.py.

Validation

• uv run ruff check packages/core/agent_framework/_tools.py packages/core/agent_framework/_mcp.py packages/core/agent_framework/_middleware.py packages/core/agent_framework/_agents.py packages/core/agent_framework/observability.py packages/core/tests/core/test_tools.py packages/core/tests/core/test_mcp.py
• uv run --directory packages/core pyright
• uv run python -m pytest -q packages/core/tests/core/test_tools.py packages/core/tests/core/test_mcp.py packages/core/tests/core/test_function_invocation_logic.py packages/core/tests/core/test_middleware.py packages/core/tests/core/test_middleware_context_result.py

[markwallace-microsoft]

Python Test Coverage Report •

File	Stmts	Miss	Cover	Missing
packages/ag-ui/agent_framework_ag_ui
_client.py	151	17	88%	85–86, 90–94, 98–102, 265, 295, 464–466
_utils.py	100	1	99%	74
packages/core/agent_framework
_agents.py	312	39	87%	476, 876, 912, 989–992, 1056–1058, 1172, 1185, 1198, 1204, 1240, 1242, 1251–1256, 1261, 1263, 1269–1270, 1277, 1279–1280, 1288–1289, 1292–1294, 1302–1303, 1305, 1310, 1312
_mcp.py	404	63	84%	102–103, 113–118, 129, 134, 180–181, 191–196, 206–207, 259, 268, 331, 339, 474, 541, 576, 578, 582–583, 585–586, 640, 655, 673, 714, 819, 832–837, 859, 905–906, 912–914, 933, 958–959, 963–967, 984–988, 1132
_middleware.py	329	16	95%	80, 83, 88, 795, 797, 799, 920, 947, 949, 974, 1055, 1059, 1183, 1187, 1248, 1322
_tools.py	817	113	86%	172–173, 310, 312, 330–332, 339, 357, 371, 378, 385, 401, 403, 410, 447, 472, 476, 493–495, 544–546, 609, 631, 655–681, 716, 727–738, 760–762, 767, 771, 785–787, 826, 895, 905, 915, 971, 1002, 1021, 1283, 1340, 1344, 1360, 1431–1435, 1453, 1455–1456, 1568, 1572, 1622, 1624, 1640, 1642, 1706, 1733, 1790, 1858, 2037–2038, 2065, 2073, 2086, 2096–2097, 2132, 2188, 2220
observability.py	618	84	86%	335, 337–339, 342–344, 349–350, 356–357, 363–364, 371, 373–375, 378–380, 385–386, 392–393, 399–400, 407, 676, 679, 687–688, 691–694, 696, 699–701, 704–705, 733, 735, 746–748, 750–753, 757, 765, 866, 868, 1017, 1019, 1023–1028, 1030, 1033–1037, 1039, 1151–1152, 1154, 1211–1212, 1347, 1401–1402, 1518–1520, 1579, 1749, 1903, 1905
packages/orchestrations/agent_framework_orchestrations
_handoff.py	326	56	82%	104–105, 107, 136–137, 159–169, 171, 173, 175, 180, 278, 331, 356, 384, 392–393, 407, 458–459, 491, 531–533, 538–540, 656, 659, 666, 671, 733, 738, 745, 755, 757, 776, 778, 860–861, 893–894, 976, 983, 1055–1056, 1058
TOTAL	20532	3275	84%

Python Unit Test Overview

Tests	Skipped	Failures	Errors	Time
3923	225 💤	0 ❌	0 🔥	1m 12s ⏱️

[Copilot]

Pull request overview

This PR attempts to optimize FunctionTool and MCP integration by passing JSON schemas directly without converting them to Pydantic models. The goal is to improve performance by skipping expensive Pydantic model creation and validation. However, the implementation has a critical bug that breaks the main agent execution path.

Changes:

• Modified FunctionTool to store JSON schemas as-is and skip Pydantic conversion when schemas are supplied
• Updated _get_input_model_from_mcp_tool and _get_input_model_from_mcp_prompt to return dicts instead of Pydantic models
• Added comprehensive test suite to verify schema passthrough behavior

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 11 comments.

File	Description
python/packages/core/agent_framework/_tools.py	Added _schema_supplied flag and _input_schema field to store JSON schemas as-is; modified _resolve_input_model to return EmptyInputModel for schema-supplied tools; updated invoke() and parameters() to handle schema passthrough
python/packages/core/agent_framework/_mcp.py	Changed _get_input_model_from_mcp_tool to return dict instead of Pydantic model; updated _get_input_model_from_mcp_prompt to return dict for prompts with arguments; removed unused import
python/packages/core/tests/core/test_mcp.py	Updated tests to expect dict schemas instead of Pydantic models; simplified test assertions to verify schema passthrough
python/packages/core/tests/core/test_schema_passthrough.py	Added 9 new tests covering schema storage, invocation, MCP integration, and performance; tests verify that JSON schemas are preserved without Pydantic conversion