do a real check

Author: mikeldking

js/packages/openinference-instrumentation-langchain/src/utils.ts

@@ -497,12 +497,19 @@ function formatPromptTemplate(run: Run): PromptTemplateAttributes | null {
 function getTokenCount(maybeCount: unknown) {
   return isNumber(maybeCount) ? maybeCount : undefined;
 }
+
 /**
- * A simple function that determines if a string is JSON like
- * Note this is a rough check just to set the MIME type
+ * A function that determines if a string is JSON like
+ * @param str - The string to check
+ * @returns true if the string is JSON
  */
 function isJSONString(str: string) {
-  return str.startsWith("{") && str.endsWith("}");
+  try {
+    JSON.parse(str);
+    return true;
+  } catch {
+    return false;
+  }
 }
 
 /**