From c4c5a4a01e05a8d18e0bf14ac92c43e60e517ea7 Mon Sep 17 00:00:00 2001
From: Parth Sareen <parth.sareen@ollama.com>
Date: Tue, 14 Oct 2025 19:35:15 -0700
Subject: [PATCH] types: send index for tool calls (#12625)

---
 api/types.go      |  2 +-
 api/types_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/api/types.go b/api/types.go
index 85a4887764..1483c844fc 100644
--- a/api/types.go
+++ b/api/types.go
@@ -204,7 +204,7 @@ type ToolCall struct {
 }
 
 type ToolCallFunction struct {
-	Index     int                       `json:"index,omitempty"`
+	Index     int                       `json:"index"`
 	Name      string                    `json:"name"`
 	Arguments ToolCallFunctionArguments `json:"arguments"`
 }
diff --git a/api/types_test.go b/api/types_test.go
index 5393b46230..5053c16210 100644
--- a/api/types_test.go
+++ b/api/types_test.go
@@ -298,6 +298,30 @@ func TestToolFunction_UnmarshalJSON(t *testing.T) {
 	}
 }
 
+func TestToolCallFunction_IndexAlwaysMarshals(t *testing.T) {
+	fn := ToolCallFunction{
+		Name:      "echo",
+		Arguments: ToolCallFunctionArguments{"message": "hi"},
+	}
+
+	data, err := json.Marshal(fn)
+	require.NoError(t, err)
+
+	raw := map[string]any{}
+	require.NoError(t, json.Unmarshal(data, &raw))
+	require.Contains(t, raw, "index")
+	assert.Equal(t, float64(0), raw["index"])
+
+	fn.Index = 3
+	data, err = json.Marshal(fn)
+	require.NoError(t, err)
+
+	raw = map[string]any{}
+	require.NoError(t, json.Unmarshal(data, &raw))
+	require.Contains(t, raw, "index")
+	assert.Equal(t, float64(3), raw["index"])
+}
+
 func TestPropertyType_UnmarshalJSON(t *testing.T) {
 	tests := []struct {
 		name     string