Handle function call messages with empty content (#203)

* Handle function call messages with empty content

* Resolve test failure

* Create heavy-yaks-mate.md

---------

Co-authored-by: Dominik Kundel <[email protected]>

Author: gilbertl

.changeset/heavy-yaks-mate.md

@@ -0,0 +1,5 @@
+---
+"@openai/agents-openai": patch
+---
+
+Handle function call messages with empty content in Chat Completions

packages/agents-openai/src/openaiChatCompletionsModel.ts

@@ -67,7 +67,13 @@ export class OpenAIChatCompletionsModel implements Model {
     const output: protocol.OutputModelItem[] = [];
     if (response.choices && response.choices[0]) {
       const message = response.choices[0].message;
-      if (message.content !== undefined && message.content !== null) {
+      
+      if (
+        message.content !== undefined &&
+        message.content !== null &&
+        // Azure OpenAI returns empty string instead of null for tool calls, causing parser rejection
+        !(message.tool_calls && message.content === '')
+      ) {
         const { content, ...rest } = message;
         output.push({
           id: response.id,