--- a/docs/configuration/outbound/urltest.md
+++ b/docs/configuration/outbound/urltest.md
@@ -10,6 +10,9 @@
     "proxy-b",
     "proxy-c"
   ],
+  "costs": {
+    "proxy-c": 100
+  },
   "url": "",
   "interval": "",
   "tolerance": 0,
@@ -26,6 +29,14 @@
 
 List of outbound tags to test.
 
+#### costs
+
+A map of outbound tag to additional latency penalty in milliseconds.
+
+The penalty is added to the measured latency when selecting the best outbound. This allows deprioritizing certain outbounds without removing them from the test group.
+
+For example, `{"proxy-c": 100}` adds 100ms to `proxy-c`'s measured latency, making it less likely to be selected unless it is significantly faster than other outbounds.
+
 #### url
 
 The URL to test. `https://www.gstatic.com/generate_204` will be used if empty.