diff --git a/doc/mdbook-metrics/Cargo.toml b/doc/mdbook-metrics/Cargo.toml
index ba6583c62361d..984c9b09a4e64 100644
--- a/doc/mdbook-metrics/Cargo.toml
+++ b/doc/mdbook-metrics/Cargo.toml
@@ -5,4 +5,5 @@ edition = "2021"
 
 [dependencies]
 mdbook = { version = "^0.4" }
+mdbook-linkcheck = "0.7.7"
 serde_json = "1.0.132"
diff --git a/doc/src/challenges/0007-atomic-types.md b/doc/src/challenges/0007-atomic-types.md
index eecaf24f5b37e..43a19f805a382 100644
--- a/doc/src/challenges/0007-atomic-types.md
+++ b/doc/src/challenges/0007-atomic-types.md
@@ -87,14 +87,18 @@ Write and verify safety contracts for the unsafe functions:
 - `atomic_umax`
 - `atomic_umin`
 
+##### Panicking (Optional)
 Then, for each of the safe abstractions that invoke the unsafe functions listed above, write contracts that ensure that they are not invoked with `order`s that would cause panics.
 
 For example, `atomic_store` panics if invoked with `Acquire` or `AcqRel` ordering.
 In this case, you would write contracts on the safe `store` methods that enforce that they are not called with either of those `order`s.
 
+This section is not required to complete the challenge, since panicking is not undefined behavior.
+However, it would be incorrect for someone to call these functions with the wrong arguments, so we encourage providing these specifications.
+
 #### Part 3: Atomic Intrinsics
 
-Write and verify safety contracts for the intrinsics invoked by the unsafe functions from Part 2 (in `core::intrinsics`):
+Write safety contracts for the intrinsics invoked by the unsafe functions from Part 2 (in `core::intrinsics`):
 
 | Operations            |  Functions |
 |-----------------------|-------------|