refactor: 正确处理 assistant 消息中的工具调用

Co-authored-by: aider (vertex_ai/gemini-2.5-pro) <aider@aider.chat>

Author: Dango233

packages/mcp-server/src/gemini-client.ts

@@ -73,8 +73,42 @@ export class GeminiApiClient {
    * 将 OpenAI 格式的消息转换为 Gemini 格式的 Content 对象。
    */
   private openAIMessageToGemini(msg: OpenAIMessage): Content {
-    const role = msg.role === 'assistant' ? 'model' : 'user';
+    // Handle assistant messages, which can contain both text and tool calls
+    if (msg.role === 'assistant') {
+      const parts: Part[] = [];
 
+      // Handle text content. It can be null when tool_calls are present.
+      if (msg.content && typeof msg.content === 'string') {
+        parts.push({ text: msg.content });
+      }
+
+      // Handle tool calls
+      if (msg.tool_calls && Array.isArray(msg.tool_calls)) {
+        for (const toolCall of msg.tool_calls) {
+          if (toolCall.type === 'function' && toolCall.function) {
+            try {
+              // Gemini API's functionCall.args expects an object, not a string.
+              // OpenAI's arguments is a JSON string, so it needs to be parsed.
+              const argsObject = JSON.parse(toolCall.function.arguments);
+              parts.push({
+                functionCall: {
+                  name: toolCall.function.name,
+                  args: argsObject,
+                },
+              });
+            } catch (e) {
+              console.error(
+                '[GeminiApiClient] Error parsing tool call arguments:',
+                e,
+              );
+            }
+          }
+        }
+      }
+      return { role: 'model', parts };
+    }
+
+    // Handle tool responses
     if (msg.role === 'tool') {
       const functionName = this.parseFunctionNameFromId(msg.tool_call_id || '');
       let responsePayload: Record<string, unknown>;
@@ -114,6 +148,9 @@ export class GeminiApiClient {
       };
     }
 
+    // Handle user and system messages
+    const role = 'user'; // system and user roles are mapped to 'user'
+
     if (typeof msg.content === 'string') {
       return { role, parts: [{ text: msg.content }] };
     }

packages/mcp-server/src/types.ts

@@ -14,20 +14,42 @@ export interface MessageContentPart {
   };
 }
 
+// OpenAI 工具调用对象
+export interface OpenAIToolCall {
+  id: string;
+  type: 'function';
+  function: {
+    name: string;
+    arguments: string; // 这是一个 JSON 字符串
+  };
+}
+
 // OpenAI 请求体中的消息对象
 export interface OpenAIMessage {
   role: 'system' | 'user' | 'assistant' | 'tool';
-  content: string | MessageContentPart[];
-  tool_calls?: any; // 根据需要定义更精确的类型
+  content: string | null | MessageContentPart[]; // 当 tool_calls 存在时，content 可能为 null
+  tool_calls?: OpenAIToolCall[];
   tool_call_id?: string;
 }
 
+// OpenAI 工具定义
+export interface OpenAIFunction {
+  name: string;
+  description?: string;
+  parameters: Record<string, unknown>; // JSON Schema object
+}
+
+export interface OpenAITool {
+  type: 'function';
+  function: OpenAIFunction;
+}
+
 // OpenAI Chat Completion 请求体
 export interface OpenAIChatCompletionRequest {
   model: string;
   messages: OpenAIMessage[];
   stream?: boolean;
-  tools?: any[]; // 对应 Gemini 的 Tool[]
+  tools?: OpenAITool[]; // 对应 Gemini 的 Tool[]
   tool_choice?: any; // 对应 Gemini 的 ToolConfig
 }