DOC Add scoring metric info in cross_val_score
@@ -281,7 +281,13 @@ def cross_val_score(estimator, X, y=None, groups=None, scoring=None, cv='warn',
scoring : string, callable or None, optional, default: None
A string (see model evaluation documentation) or
a scorer callable object / function with signature
- ``scorer(estimator, X, y)``.
+ ``scorer(estimator, X, y)`` which should return only
+ a single value.
+
+ Similar to :func:`cross_validate`
+ but only a single metric is permitted.
+
+ If None, the estimator's default scorer (if available) is used.
cv : int, cross-validation generator or an iterable, optional
Determines the cross-validation splitting strategy.
