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: internal-only (bug fix to unexported parsing logic; no exported API surface added or changed)

Changed Go contract: None. provider/geminiprovider/agent.go's unexported buildResponsePart now also reads part.ToolCall / part.ToolResponse and emits already-existing exported types message.FunctionCallContent{InformationalOnly: true} and message.FunctionResultContent. No new exported functions, types, fields, or options were introduced; InformationalOnly on FunctionCallContent already existed and is already respected by agent/harness/toolautocall (e.g. autocall.go:301,446,726).

Upstream evidence reviewed: python/packages/gemini/agent_framework_gemini/_chat_client.py, method _parse_parts (lines ~1194-1246):

• part.tool_call is not None → builds a FunctionCallContent-equivalent with informational_only=True, tool_name from tool_call.tool_type (falls back to "tool_call"), and a generated call_id via _generate_tool_call_id() when missing.
• part.tool_response is not None → builds a function-result-equivalent with call_id=tool_response.id or self._generate_tool_call_id() and result=tool_response.response.

The Go change (provider/geminiprovider/agent.go) mirrors this mapping symbol-for-symbol: part.ToolCall → FunctionCallContent{Name: string(ToolType) or "tool_call", InformationalOnly: true, CallID: ID or generated}, and part.ToolResponse → FunctionResultContent{CallID: ID or generated, Result: Response}.

Result: Aligned. This closes a genuine parity gap (Go was previously silently dropping these parts while Python already surfaced them) and does not introduce any exported Go API or new user-configurable behavior — the new content is instances of existing public types and is correctly treated as non-executable via the existing InformationalOnly short-circuit in toolautocall. No inline findings; no public-api-change label needed.

Generated by Go API Consistency Review Agent · copilot · auto · 20.4 AIC · ⌖ 6.14 AIC · ⊞ 9.2K · ◷