diff --git a/librustzcash/src/rustzcash.rs b/librustzcash/src/rustzcash.rs
index 98c9ff7..068fb77 100644
--- a/librustzcash/src/rustzcash.rs
+++ b/librustzcash/src/rustzcash.rs
@@ -1,3 +1,7 @@
+//! FFI between the C++ zcashd codebase and the Rust Zcash crates.
+//!
+//! This is internal to zcashd and is not an officially-supported API.
+
 // Catch documentation errors caused by code changes.
 #![deny(intra_doc_link_resolution_failure)]
 // Clippy has a default-deny lint to prevent dereferencing raw pointer arguments