diff --git a/owm_api25/src/query.rs b/owm_api25/src/query.rs
index 67fc65d..c1db86a 100644
--- a/owm_api25/src/query.rs
+++ b/owm_api25/src/query.rs
@@ -36,12 +36,22 @@ pub struct QueryParams {
 }
 
 impl QueryParams {
-    /// Build query URL for the `/weather` endpoint
+    /// Build query URL for the `/weather` endpoint.
+    ///
+    /// # Errors
+    ///
+    /// Returns an `Err` if no valid location is specified
+    /// (e.g., `city_id`, `city_name`, `lat`/`lon`, or `zip` are all `None`).
     pub fn weather_url(&self) -> Result<String, String> {
         self.build_url(WEATHER_URL)
     }
 
-    /// Build query URL for the `/forecast` endpoint
+    /// Build query URL for the `/forecast` endpoint.
+    ///
+    /// # Errors
+    ///
+    /// Returns an `Err` if no valid location is specified
+    /// (e.g., `city_id`, `city_name`, `lat`/`lon`, or `zip` are all `None`).
     pub fn forecast_url(&self) -> Result<String, String> {
         self.build_url(FORECAST_URL)
     }