feat(models): add tool use support to OpenAIClient

src/models/openai.ts

@@ -33,15 +33,36 @@ export class OpenAIClient implements ModelClient {
       messages.push({ role: msg.role, content: msg.content });
     }
 
-    const response = await this.client.chat.completions.create({
+    // Build params, conditionally including tools
+    const params: OpenAI.ChatCompletionCreateParamsNonStreaming = {
       model: this.model,
       max_tokens: request.maxTokens ?? this.defaultMaxTokens,
       messages,
-    });
+    };
+
+    if (request.tools && request.tools.length > 0) {
+      params.tools = request.tools.map(t => ({
+        type: 'function' as const,
+        function: {
+          name: t.name,
+          description: t.description,
+          parameters: t.input_schema as OpenAI.FunctionParameters,
+        },
+      }));
+    }
+
+    const response = await this.client.chat.completions.create(params);
 
     const choice = response.choices[0];
     const content = choice?.message?.content ?? '';
 
+    // Parse tool_calls from the response if present
+    const toolCalls = choice?.message?.tool_calls?.map((tc: OpenAI.ChatCompletionMessageToolCall) => ({
+      id: tc.id,
+      name: tc.function.name,
+      args: JSON.parse(tc.function.arguments),
+    })) ?? [];
+
     return {
       content,
       stopReason: choice?.finish_reason ?? 'stop',
@@ -49,6 +70,7 @@ export class OpenAIClient implements ModelClient {
         inputTokens: response.usage?.prompt_tokens ?? 0,
         outputTokens: response.usage?.completion_tokens ?? 0,
       },
+      ...(toolCalls.length > 0 ? { toolCalls } : {}),
     };
   }
 }