diff --git a/shlink.py b/shlink.py
index c5ff349..fc94d55 100644
--- a/shlink.py
+++ b/shlink.py
@@ -1,10 +1,7 @@
-"""Shlink short-URL client.
-
+"""
+Shlink short-URL client.
 Provides a single async helper, ``shorten(url)``, that calls the Shlink
-REST API and returns the shortened URL. Returns the original URL unchanged
-on any error.
-
-Requires: httpx
+REST API via httpx. Returns the original URL unchanged on any error.
 """
 
 import logging
@@ -23,23 +20,44 @@ class ShlinkClient:
 
     async def shorten(self, url: str) -> str:
         """Return a shortened URL, or ``url`` unchanged on failure."""
-        payload = {"longUrl": url, "findIfExists": True}
+        payload = {
+            "longUrl": url,
+            "findIfExists": True
+        }
         if self._domain:
             payload["domain"] = self._domain
 
-        headers = {"X-Api-Key": self._api_key, "Content-Type": "application/json"}
+        headers = {
+            "X-Api-Key": self._api_key,
+            "Content-Type": "application/json",
+        }
 
         try:
             async with httpx.AsyncClient(timeout=self._timeout) as client:
                 resp = await client.post(self._endpoint, json=payload, headers=headers)
                 resp.raise_for_status()
-                return resp.json()["shortUrl"]
+                data = resp.json()
+                
+                short = data["shortUrl"]
+                log.debug("Shortened %s → %s", url, short)
+                return short
         except Exception as e:
             log.warning("Shlink error for %s: %s", url, e)
             return url
 
 def from_config(cfg: dict) -> "ShlinkClient | None":
-    if not cfg.get("enabled", True): return None
-    base, api_key = cfg.get("url", "").strip(), cfg.get("api_key", "").strip()
-    if not base or not api_key: return None
-    return ShlinkClient(base, api_key, int(cfg.get("timeout", 5)), cfg.get("domain"))
+    """Build a ShlinkClient from the [shlink] config section."""
+    if not cfg.get("enabled", True):
+        return None
+    base = cfg.get("url", "").strip()
+    api_key = cfg.get("api_key", "").strip()
+    if not base or not api_key:
+        if base or api_key:
+            log.warning("[shlink] Both 'url' and 'api_key' are required — disabling")
+        return None
+    return ShlinkClient(
+        base_url=base,
+        api_key=api_key,
+        timeout=int(cfg.get("timeout", 5)),
+        domain=cfg.get("domain") or None,
+    )