Surface Gemini server-side tool-call and tool-response parts

[PratikDhanave (PratikDhanave)]

Gemini can echo back server-side tool invocations as toolCall / toolResponse response parts (e.g. when a function tool is combined with a native tool). buildResponsePart only handled Thought, Text, FunctionCall, InlineData, FileData, ExecutableCode, and CodeExecutionResult — it never read part.ToolCall or part.ToolResponse, so those parts were silently dropped and the caller never observed the model's server-side tool interactions.

The Python client (_parse_parts) maps both: tool_call → a function call with informational_only=True, tool_response → a function result.

Change

• Map part.ToolCall → FunctionCallContent{InformationalOnly: true} — surfaced so callers can observe it, but marked informational so the tool-call loop does not try to execute a call the server already ran (toolautocall skips InformationalOnly calls).
• Map part.ToolResponse → FunctionResultContent.
• Tool name comes from ToolType (fallback "tool_call"); missing call ids are synthesized like the existing FunctionCall path.

Test

• TestServerSideToolCallAndResponsePartsSurfaced: a candidate carrying a toolCall and a toolResponse now surfaces an informational-only FunctionCallContent and a FunctionResultContent. Fails before the change (both dropped), passes after.

[Copilot]

Copilot review overview

🟡 Changes recommended

Address call-ID correlation and ThoughtSignature preservation; strengthen the response-payload assertion.

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Review effort: Lite
Findings: 1

Open (1)

• Reuse tool call ID when generating a missing response ID · New

What changed in this PR

Surfaces Gemini server-side tool calls and responses as framework function content.

Changes:

• Maps ToolCall to informational-only function calls.
• Maps ToolResponse to function results.
• Adds regression coverage for both mappings.

File	Summary
provider/​geminiprovider/​agent.go	Converts server-side tool parts into framework content.
provider/​geminiprovider/​agent_test.go	Tests surfaced tool calls and responses.

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[github-actions]

Scope: user-visible behavior, internal-only
Changed Go contract: None exported. buildResponsePart (unexported) now maps genai.Part.ToolCall → message.FunctionCallContent{InformationalOnly: true} and genai.Part.ToolResponse → message.FunctionResultContent; responsePartState (unexported) gained a pendingToolCallID field to correlate a response lacking its own id with the preceding call.
Upstream evidence reviewed: python/packages/gemini/agent_framework_gemini/_chat_client.py _parse_parts (lines ~1194-1240): maps part.tool_call → Content.from_function_call(..., informational_only=True) and part.tool_response → Content.from_function_result(call_id=tool_response.id or generated, result=tool_response.response). No .NET Gemini provider exists upstream (dotnet/src/Microsoft.Agents.AI.*), so Python is the sole parity reference for this integration.
Result: aligned

The Go change mirrors the Python _parse_parts semantics: server-side tool calls are surfaced as informational-only function calls (so toolautocall skips re-executing them — confirmed via agent/harness/toolautocall/autocall.go checks on InformationalOnly), and tool responses surface as function results. This closes a real bug (these parts were previously silently dropped in Go).

One minor, non-blocking observation: when a tool_response omits its own id, Go correlates it with the immediately preceding tool call's id (pendingToolCallID) before falling back to a synthesized id, whereas Python's _parse_parts always generates an independent random id in that case with no correlation fallback. This makes Go's edge-case behavior more correct/consistent than Python's (verified by the added TestServerSideToolResponseInheritsCallID test), not a regression, so it isn't flagged as a parity defect — just noting the intentional, beneficial divergence for future reference.

No exported Go API surface changed (both touched symbols are unexported), so public-api-change is not applicable.

Generated by Go API Consistency Review Agent · copilot · auto · 59.6 AIC · ⌖ 8.05 AIC · ⊞ 9.2K · ◷