Python: Strip tools from Foundry agent request on the preview path (allow_preview=True)

[vaibhav-patel]

Summary

FoundryAgent / RawFoundryAgentChatClient still returns HTTP 400 invalid_payload
("Not allowed when agent is specified.", param tools) when tools are passed and
allow_preview=True.

PR #5101 added stripping of tools / tool_choice / parallel_tool_calls in
RawFoundryAgentChatClient._prepare_options(), but gated it behind
if not self.allow_preview:. The preview path also specifies an agent — the identity
is bound on the OpenAI client via project_client.get_openai_client(agent_name=...) —
so tool declarations are still rejected there. Since agent_name is required for this
client, it always targets a pre-provisioned agent and must never send tools.

Changes

• Remove the allow_preview gate so tool fields are stripped from the request body on
  both the preview and non-preview paths.
• Emit a single logger.warning when the caller supplied tools, clarifying they are
  used only for client-side function dispatch and that tool schemas must live on the
  agent definition in the service.
• Tests: extend the existing strip test to assert the warning; add a regression test for
  the allow_preview=True path and a test that no warning is emitted when no tools are
  passed.

The model-based FoundryChatClient (no agent_reference) is unaffected — it still
sends tools.

Testing

• uv run pytest packages/foundry/tests/foundry/test_foundry_agent.py → 51 passed,
  3 skipped (live-Azure integration tests).

Fixes #5130.

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[Copilot]

Pull request overview

This PR fixes Foundry agent requests failing with HTTP 400 invalid_payload when callers provide tools while using the hosted-agent “preview” path (allow_preview=True). Since RawFoundryAgentChatClient always targets a pre-provisioned Foundry agent (agent identity is specified either via extra_body.agent_reference or via the OpenAI client’s agent_name binding), the client must never send tool declarations in the request body.

Changes:

• Always strip tools, tool_choice, and parallel_tool_calls from the outgoing request options (preview and non-preview paths).
• Emit a single warning when tool declarations are provided, clarifying they’re only used for client-side function dispatch.
• Extend/add unit tests to cover the warning behavior and the allow_preview=True regression.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
python/packages/foundry/agent_framework_foundry/_agent.py	Removes the preview-only gate so tool-related fields are always stripped; adds a warning when tools are dropped.
python/packages/foundry/tests/foundry/test_foundry_agent.py	Updates/extends tests to assert warning emission, adds regression coverage for allow_preview=True, and validates no warning when no tools are provided.