fix(tools): adapt tool prompt framing to ensure reliable tool calls in persona spaces

gr2gw_test.go

@@ -534,7 +534,7 @@ func TestUniversalToolCallingTransformMessages(t *testing.T) {
     t.Fatalf("expected 4 processed messages, got %d", len(processed))
   }
 
-  if processed[0].Role != "system" || !strings.Contains(processed[0].GetContentString(), "Tool Calling Instructions") {
+  if processed[0].Role != "system" || !strings.Contains(processed[0].GetContentString(), "API router") {
     t.Errorf("unexpected message 0: %+v", processed[0])
   }
 
@@ -701,7 +701,7 @@ func TestBuildGradioPayloadGenericSpaces(t *testing.T) {
     t.Fatalf("failed to build payload 1: %v", err)
   }
   sysStr, ok := data1[0].(string)
-  if !ok || !strings.Contains(sysStr, "Tool Calling Instructions") {
+  if !ok || !strings.Contains(sysStr, "API router") {
     t.Errorf("expected system prompt at index 0, got %v", data1[0])
   }
   msgStr, ok := data1[1].(string)
@@ -733,7 +733,7 @@ func TestBuildGradioPayloadGenericSpaces(t *testing.T) {
     t.Fatalf("expected 1 history pair at index 1, got %T (%v)", data2[1], data2[1])
   }
   // Instructions prepended to the first user turn:
-  if !strings.Contains(pairs2[0][0], "Tool Calling Instructions") || !strings.Contains(pairs2[0][0], "What is 10+10?") {
+  if !strings.Contains(pairs2[0][0], "API router") || !strings.Contains(pairs2[0][0], "What is 10+10?") {
     t.Errorf("expected system instructions prepended to first pair user message, got: %q", pairs2[0][0])
   }
   if !strings.Contains(pairs2[0][1], "lookup") {
@@ -1249,7 +1249,7 @@ func TestSystemPromptAugmentationWithoutNativeToolCalling(t *testing.T) {
   if !strings.Contains(sysStr, "You are a specialized documentation bot.") {
     t.Errorf("expected default system prompt to be retained, got: %s", sysStr)
   }
-  if !strings.Contains(sysStr, "Tool Calling Instructions") || !strings.Contains(sysStr, "search_docs") {
+  if !strings.Contains(sysStr, "API router") || !strings.Contains(sysStr, "search_docs") {
     t.Errorf("expected tool calling instructions and function name in system prompt, got: %s", sysStr)
   }
 
@@ -1291,10 +1291,42 @@ func TestSystemPromptAugmentationWithoutNativeToolCalling(t *testing.T) {
   if !ok {
     t.Fatalf("expected string at index 0, got %T", payload3[0])
   }
-  if !strings.Contains(singleMsg, "Tool Calling Instructions") || !strings.Contains(singleMsg, "How to configure SSL?") {
+  if !strings.Contains(singleMsg, "API router") || !strings.Contains(singleMsg, "How to configure SSL?") {
     t.Errorf("expected single message to contain augmented instructions and user query, got: %s", singleMsg)
   }
 }
 
+func TestToolChoiceHandling(t *testing.T) {
+  tools := []Tool{
+    {
+      Type: "function",
+      Function: map[string]interface{}{
+        "name":        "calculator",
+        "description": "Evaluate math expression",
+      },
+    },
+  }
 
+  // 1. ToolChoice: "none" -> no tool instruction generated
+  instrNone := BuildToolInstruction(tools, "none")
+  if instrNone != "" {
+    t.Errorf("expected empty instruction for tool_choice: none, got: %s", instrNone)
+  }
 
+  // 2. ToolChoice: "required" -> mandatory directive
+  instrReq := BuildToolInstruction(tools, "required")
+  if !strings.Contains(instrReq, "You MUST call one of the available tools") {
+    t.Errorf("expected required directive in instruction, got: %s", instrReq)
+  }
+
+  // 3. ToolChoice: specific function
+  instrFn := BuildToolInstruction(tools, map[string]interface{}{
+    "type": "function",
+    "function": map[string]interface{}{
+      "name": "calculator",
+    },
+  })
+  if !strings.Contains(instrFn, "You MUST call the calculator tool") {
+    t.Errorf("expected specific function directive in instruction, got: %s", instrFn)
+  }
+}