diff --git a/components/style/values/animated/mod.rs b/components/style/values/animated/mod.rs
index ad81a4ecc4a..9e0653d8a00 100644
--- a/components/style/values/animated/mod.rs
+++ b/components/style/values/animated/mod.rs
@@ -35,6 +35,9 @@ pub mod effects;
 ///
 /// If the two values are not similar, an error is returned unless a fallback
 /// function has been specified through `#[animate(fallback)]`.
+///
+/// Trait bounds for type parameter `Foo` can be opted out of with
+/// `#[animation(no_bound(Foo))]` on the type definition.
 pub trait Animate: Sized {
     /// Animate a value towards another one, given an animation procedure.
     fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()>;
@@ -78,6 +81,9 @@ pub trait ToAnimatedValue {
 ///
 /// If a variant is annotated with `#[animation(error)]`, the corresponding
 /// `match` arm is not generated.
+///
+/// Trait bounds for type parameter `Foo` can be opted out of with
+/// `#[animation(no_bound(Foo))]` on the type definition.
 pub trait ToAnimatedZero: Sized {
     /// Returns a value that, when added with an underlying value, will produce the underlying
     /// value. This is used for SMIL animation's "by-animation" where SMIL first interpolates from
diff --git a/components/style/values/distance.rs b/components/style/values/distance.rs
index f17b9931dda..5f84f17caad 100644
--- a/components/style/values/distance.rs
+++ b/components/style/values/distance.rs
@@ -21,6 +21,10 @@ use std::ops::Add;
 ///
 /// If the two values are not similar, an error is returned unless a fallback
 /// function has been specified through `#[distance(fallback)]`.
+///
+/// Trait bounds for type parameter `Foo` can be opted out of with
+/// `#[animation(no_bound(Foo))]` on the type definition, trait bounds for
+/// fields can be opted into with `#[distance(field_bound)]` on the field.
 pub trait ComputeSquaredDistance {
     /// Computes the squared distance between two animatable values.
     fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()>;