Response.ToolCalls

ToolCalls extracts the ToolCall parts from the assistant's message. It is shorthand for Response.Message.ToolCalls().

Reference#

func (r *Response) ToolCalls() []ToolCall

Returns

Every tool call in the order the model produced them. Returns nil when there are none, so a plain range is safe without a length check.

Caveats

Nil-safe on a nil *Response.
On Gemini, ToolCall.ID is the function name, because Gemini issues no call IDs. Two parallel calls to the same tool are therefore indistinguishable by ID — pair results by position instead.
Arguments is json.RawMessage; skyl cannot know your tool's schema.
It flattens ordering against text. Use Message.Parts when the interleaving matters.

Usage#

Running the calls

goCompiles

for _, call := range resp.ToolCalls() {
	var args struct {
		City string `json:"city"`
	}
	if err := json.Unmarshal(call.Arguments, &args); err != nil {
		req.Messages = append(req.Messages,
			skyl.ToolErrorMessage(call.ID, "could not parse arguments: "+err.Error()))
		continue
	}
	req.Messages = append(req.Messages,
		skyl.ToolResultMessage(call.ID, weather(args.City)))
}

for _, call := range resp.ToolCalls() {
	var args struct {
		City string `json:"city"`
	}
	if err := json.Unmarshal(call.Arguments, &args); err != nil {
		req.Messages = append(req.Messages,
			skyl.ToolErrorMessage(call.ID, "could not parse arguments: "+err.Error()))
		continue
	}
	req.Messages = append(req.Messages,
		skyl.ToolResultMessage(call.ID, weather(args.City)))
}

Detecting the end of a tool loop

goCompiles

// More reliable than StopReason: on Gemini, any function call forces
// StopToolUse regardless of the actual finishReason.
if len(resp.ToolCalls()) == 0 {
	return resp, nil
}

// More reliable than StopReason: on Gemini, any function call forces
// StopToolUse regardless of the actual finishReason.
if len(resp.ToolCalls()) == 0 {
	return resp, nil
}

Pairing results safely on every provider

goCompiles

calls := resp.ToolCalls()
results := make([]string, len(calls))
for i, call := range calls {
	results[i] = run(call) // indexed, so identical Gemini IDs cannot collide
}

req.Messages = append(req.Messages, resp.Message)
for i, call := range calls {
	req.Messages = append(req.Messages, skyl.ToolResultMessage(call.ID, results[i]))
}

calls := resp.ToolCalls()
results := make([]string, len(calls))
for i, call := range calls {
	results[i] = run(call) // indexed, so identical Gemini IDs cannot collide
}

req.Messages = append(req.Messages, resp.Message)
for i, call := range calls {
	req.Messages = append(req.Messages, skyl.ToolResultMessage(call.ID, results[i]))
}

Troubleshooting#

Two calls to the same tool collapsed into one

You keyed a map by call.ID and are on Gemini, where the ID is the function name. Index by position instead.

A call I expected did not appear, while streaming

On OpenAI and openaicompat, a streamed tool call whose name never arrived is silently discarded — it cannot be dispatched. Inspect StreamEvent.Raw on the preceding frames.

The provider rejected my next request with a 400

Almost always ordering: resp.Message must be appended before any tool result. Every provider rejects a result that does not follow its call.