feat(tools): augment system prompt when no native tool calling is detected

gr2gw.go

@@ -441,23 +441,44 @@ func BuildToolInstruction(tools []Tool) string {
     return ""
   }
   toolsBytes, _ := json.MarshalIndent(tools, "", "  ")
+
+  sampleFnName := ""
+  for _, t := range tools {
+    if fnMap, ok := t.Function.(map[string]interface{}); ok {
+      if n, ok := fnMap["name"].(string); ok && n != "" {
+        sampleFnName = n
+        break
+      }
+    }
+  }
+  if sampleFnName == "" {
+    sampleFnName = "example_tool"
+  }
+
   return fmt.Sprintf(`# Tool Calling Instructions
 
+You are equipped with external tools to assist with user queries.
 You have access to the following tools:
 <tools>
 %s
 </tools>
 
-To call a tool, you MUST output a <tool_call> block directly in your text response formatted exactly as follows:
+When the user asks a question or makes a request that can be fulfilled, assisted, or answered using any of the tools above, you MUST call the appropriate tool.
+DO NOT refuse to answer, and DO NOT claim that you lack real-time access, live data, or tool capabilities when a tool is provided for that purpose.
+
+## Tool Calling Syntax
+To call a tool, you MUST output a <tool_call> block formatted as:
 <tool_call>
-{"name": "<function-name>", "arguments": {<args-json-object>}}
+{"name": "%s", "arguments": {...}}
 </tool_call>
 
-Rules:
+## Rules:
-- If you need to call a tool, respond ONLY with the <tool_call> block. Do not include introductory text, explanations, or commentary around the block.
+1. If an available tool is relevant to the user's request, invoking the tool is MANDATORY.
-- If you need to call multiple tools, provide each tool call in its own <tool_call> block.
+2. When calling a tool, your ENTIRE output must consist ONLY of the <tool_call> block. Do not add introductory text, commentary, or conversational filler.
-- If no tool call is needed, answer the user's request directly and normally without using tool tags.
+3. If multiple tools are required, output each in its own <tool_call> block.
-- When you receive a <tool_response>, answer the user's request using the information provided in the response, or call another tool if additional information is required.`, string(toolsBytes))
+4. Arguments must be a valid JSON object strictly matching the tool's parameter definitions.
+5. If no tools are relevant to the user's inquiry, respond normally with plain text.
+6. When tool execution results are provided to you in subsequent turns (via <tool_response> blocks or tool role messages), formulate your final answer to the user based on those results.`, string(toolsBytes), sampleFnName)
 }
 
 func TransformMessages(req ChatCompletionRequest) (processed []ChatMessage, toolInstruction string, hasSystem bool) {
@@ -1494,9 +1515,10 @@ func (f *StreamToolCallFilter) Flush(onContent func(string), onToolCall func(Too
 // ---------------------------------------------------------------------------
 
 type GradioParamInfo struct {
-  Label         string `json:"label"`
+  Label            string      `json:"label"`
-  ParameterName string `json:"parameter_name"`
+  ParameterName    string      `json:"parameter_name"`
-  Component     string `json:"component"`
+  ParameterDefault interface{} `json:"parameter_default,omitempty"`
+  Component        string      `json:"component"`
 }
 
 type GradioEndpointInfo struct {
@@ -1574,6 +1596,7 @@ type SpaceDiscovery struct {
   HistoryIndex           int    // -1 if none
   MessageIndex           int    // index for user message text
   SystemIndex            int    // -1 if none
+  DefaultSystemPrompt    string // default space system prompt if present
   TempIndex              int    // -1 if none
   MaxTokensIndex         int    // -1 if none
   TopPIndex              int    // -1 if none
@@ -1639,6 +1662,7 @@ func NewDefaultSpaceDiscovery(spaceURL string) *SpaceDiscovery {
     HistoryIndex:           -1,
     MessageIndex:           0,
     SystemIndex:            -1,
+    DefaultSystemPrompt:    "",
     TempIndex:              -1,
     MaxTokensIndex:         -1,
     TopPIndex:              -1,
@@ -1863,6 +1887,11 @@ func InspectSpace(client *http.Client, rawURL, userAgent string) (*SpaceDiscover
             } else if discovery.SystemIndex == -1 {
               mapping.ParamType = "system_prompt"
               discovery.SystemIndex = idx
+              if comp.Props != nil {
+                if val, ok := comp.Props["value"].(string); ok && strings.TrimSpace(val) != "" {
+                  discovery.DefaultSystemPrompt = strings.TrimSpace(val)
+                }
+              }
             }
           case "state":
             mapping.ParamType = "state"
@@ -1905,6 +1934,11 @@ func InspectSpace(client *http.Client, rawURL, userAgent string) (*SpaceDiscover
       pName := strings.ToLower(p.ParameterName)
       if strings.Contains(pName, "system") {
         discovery.SystemIndex = idx
+        if p.ParameterDefault != nil && discovery.DefaultSystemPrompt == "" {
+          if defStr, ok := p.ParameterDefault.(string); ok && strings.TrimSpace(defStr) != "" {
+            discovery.DefaultSystemPrompt = strings.TrimSpace(defStr)
+          }
+        }
       } else if strings.Contains(pName, "history") || strings.Contains(pName, "chat") {
         discovery.HistoryIndex = idx
       } else if strings.Contains(pName, "message") || (strings.Contains(pName, "prompt") && !strings.Contains(pName, "system")) || strings.Contains(pName, "text") {
@@ -2038,6 +2072,7 @@ func (g *GradioGateway) GetDiscovery(spaceURL, userAgent string) *SpaceDiscovery
 // BuildGradioPayload packages OpenAI messages and parameters into the target Gradio input array.
 func (g *GradioGateway) BuildGradioPayload(disc *SpaceDiscovery, req ChatCompletionRequest) ([]interface{}, error) {
   var transformed []ChatMessage
+  var toolInstruction string
   if disc.IsHunyuan3 && disc.FunctionsJSONIndex != -1 {
     for _, msg := range req.Messages {
       transformed = append(transformed, ChatMessage{
@@ -2050,7 +2085,16 @@ func (g *GradioGateway) BuildGradioPayload(disc *SpaceDiscovery, req ChatComplet
       })
     }
   } else {
-    transformed, _, _ = TransformMessages(req)
+    // When no native tool calling support is detected, augment system prompt
+    transformed, toolInstruction, _ = TransformMessages(req)
+  }
+
+  hasClientSystem := false
+  for _, m := range req.Messages {
+    if m.Role == "system" {
+      hasClientSystem = true
+      break
+    }
   }
 
   var systemPromptStr string
@@ -2071,13 +2115,22 @@ func (g *GradioGateway) BuildGradioPayload(disc *SpaceDiscovery, req ChatComplet
     }
   }
 
+  // If the space has a DefaultSystemPrompt and client provided no system message,
+  // retain and augment the default system prompt:
+  if !hasClientSystem && disc.DefaultSystemPrompt != "" {
+    if systemPromptStr != "" {
+      systemPromptStr = disc.DefaultSystemPrompt + "\n\n" + systemPromptStr
+    } else {
+      systemPromptStr = disc.DefaultSystemPrompt
+    }
+  }
+
   // If the space has NO native system prompt input (disc.SystemIndex == -1),
   // but we have system instructions (from system message or tool instructions):
   if disc.SystemIndex == -1 && systemPromptStr != "" && len(nonSystem) > 0 {
     // If the space supports conversation history, prepend system instructions to the first turn
     if disc.HistoryIndex != -1 {
       nonSystem[0].Content = systemPromptStr + "\n\n" + nonSystem[0].GetContentString()
-      systemPromptStr = ""
     }
   }
 
@@ -2156,7 +2209,11 @@ func (g *GradioGateway) BuildGradioPayload(disc *SpaceDiscovery, req ChatComplet
 
   var promptMessageText string
   if disc.HistoryIndex != -1 {
-    promptMessageText = lastUserMessage
+    if disc.SystemIndex == -1 && len(nonSystem) > 1 && toolInstruction != "" {
+      promptMessageText = fmt.Sprintf("[System Directive: Tool calling mode active. If relevant, output a <tool_call> block.]\n\n%s", lastUserMessage)
+    } else {
+      promptMessageText = lastUserMessage
+    }
   } else {
     // Single message space: compose multi-turn history into the prompt
     if len(nonSystem) <= 1 {

gr2gw_test.go

@@ -1204,4 +1204,97 @@ func TestToolUseFailedImmediateCallRecovery(t *testing.T) {
   }
 }
 
+func TestSystemPromptAugmentationWithoutNativeToolCalling(t *testing.T) {
+  gw := NewGradioGateway("https://generic-space.hf.space", "", 10*time.Second)
+
+  tools := []Tool{
+    {
+      Type: "function",
+      Function: map[string]interface{}{
+        "name":        "search_docs",
+        "description": "Search local documentation",
+        "parameters": map[string]interface{}{
+          "type": "object",
+          "properties": map[string]interface{}{
+            "query": map[string]interface{}{"type": "string"},
+          },
+          "required": []string{"query"},
+        },
+      },
+    },
+  }
+
+  // Case 1: Space with SystemIndex and space default prompt, client sends no system message
+  discWithSys := NewDefaultSpaceDiscovery("https://generic-space.hf.space")
+  discWithSys.TotalInputs = 2
+  discWithSys.MessageIndex = 0
+  discWithSys.SystemIndex = 1
+  discWithSys.DefaultSystemPrompt = "You are a specialized documentation bot."
+
+  req1 := ChatCompletionRequest{
+    Tools: tools,
+    Messages: []ChatMessage{
+      {Role: "user", Content: "How to configure SSL?"},
+    },
+  }
+
+  payload1, err := gw.BuildGradioPayload(discWithSys, req1)
+  if err != nil {
+    t.Fatalf("BuildGradioPayload failed: %v", err)
+  }
+  sysStr, ok := payload1[1].(string)
+  if !ok {
+    t.Fatalf("expected string at SystemIndex 1, got %T", payload1[1])
+  }
+  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") {
+    t.Errorf("expected tool calling instructions and function name in system prompt, got: %s", sysStr)
+  }
+
+  // Case 2: Space with SystemIndex, client sends their own system message
+  req2 := ChatCompletionRequest{
+    Tools: tools,
+    Messages: []ChatMessage{
+      {Role: "system", Content: "You are an expert developer assistant."},
+      {Role: "user", Content: "How to configure SSL?"},
+    },
+  }
+  payload2, err := gw.BuildGradioPayload(discWithSys, req2)
+  if err != nil {
+    t.Fatalf("BuildGradioPayload failed: %v", err)
+  }
+  sysStr2, ok := payload2[1].(string)
+  if !ok {
+    t.Fatalf("expected string at SystemIndex 1, got %T", payload2[1])
+  }
+  if !strings.Contains(sysStr2, "You are an expert developer assistant.") {
+    t.Errorf("expected client system message, got: %s", sysStr2)
+  }
+  if !strings.Contains(sysStr2, "search_docs") {
+    t.Errorf("expected search_docs tool instruction, got: %s", sysStr2)
+  }
+
+  // Case 3: Space without SystemIndex, single input textbox
+  discSingle := NewDefaultSpaceDiscovery("https://single-input.hf.space")
+  discSingle.TotalInputs = 1
+  discSingle.MessageIndex = 0
+  discSingle.SystemIndex = -1
+  discSingle.HistoryIndex = -1
+
+  payload3, err := gw.BuildGradioPayload(discSingle, req1)
+  if err != nil {
+    t.Fatalf("BuildGradioPayload failed: %v", err)
+  }
+  singleMsg, ok := payload3[0].(string)
+  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?") {
+    t.Errorf("expected single message to contain augmented instructions and user query, got: %s", singleMsg)
+  }
+}
+
+