diff --git a/harvester/proxy.py b/harvester/proxy.py
index 979a611..ed5e5ce 100644
--- a/harvester/proxy.py
+++ b/harvester/proxy.py
@@ -36,6 +36,17 @@ def fetch_list(url):
 
 
 def fetch_all(urls, max_workers=8):
+    """Fetches proxy server addresses from multiple URLs concurrently.
+
+    Args:
+        urls (list): A list of URLs to fetch proxy server addresses from.
+        max_workers (int, optional): The maximum number of worker threads to use.
+            Defaults to 8.
+
+    Returns:
+        list: A list of unique proxy server addresses fetched from all the URLs.
+
+    """
     proxies = []
     with concurrent.futures.ThreadPoolExecutor(max_workers=max_workers) as executor:
         future_to_url = {executor.submit(fetch_list, url): url for url in urls}