diff --git a/ic-cdk/src/api.rs b/ic-cdk/src/api.rs
index 9c935767..c7b05074 100644
--- a/ic-cdk/src/api.rs
+++ b/ic-cdk/src/api.rs
@@ -1,4 +1,21 @@
 //! System API bindings.
+//! 
+//! This module provides Rust ergonomic bindings to the system APIs.
+//! 
+//! Some APIs require more advanced handling and are organized into separate modules:
+//! * For the inter-canister calls API, see the [`call`](crate::call) module.
+//! * For the stable memory management API, see the [`stable`](crate::stable) module.
+//! 
+//! APIs that are only available for `wasm32` are not included.
+//! As a result, system APIs with a numeric postfix (indicating the data bit width) are bound to names without the postfix.
+//! For example, `ic0::msg_cycles_available128` is bound to [`msg_cycles_available`], while `ic0::msg_cycles_available` has no binding.
+//! 
+//! Functions that provide bindings for a single system API method share the same name as the system API.
+//! For example, `ic0::msg_reject_code` is bound to [`msg_reject_code`].
+//! 
+//! Functions that wrap multiple system API methods are named using the common prefix of the wrapped methods.
+//! For example, [`msg_arg_data`] wraps both `ic0::msg_arg_data_size` and `ic0::msg_arg_data_copy`.
+
 use candid::Principal;
 use std::convert::TryFrom;
 
@@ -163,6 +180,8 @@ pub fn canister_status() -> u32 {
 }
 
 /// Gets the canister version.
+/// 
+/// See [Canister version](https://internetcomputer.org/docs/current/references/ic-interface-spec/#system-api-canister-version).
 pub fn canister_version() -> u64 {
     // SAFETY: ic0.canister_version is always safe to call.
     unsafe { ic0::canister_version() }
@@ -217,7 +236,7 @@ pub fn certified_data_set(data: &[u8]) {
 /// When called from a query call, returns the data certificate authenticating
 /// certified_data set by this canister.
 ///
-/// Returns None if called not from a query call.
+/// Returns `None` if called not from a query call.
 pub fn data_certificate() -> Option<Vec<u8>> {
     // SAFETY: ic0.data_certificate_present is always safe to call.
     if unsafe { ic0::data_certificate_present() } == 0 {