diff --git a/gear-programs/historical-proxy/app/src/lib.rs b/gear-programs/historical-proxy/app/src/lib.rs
index f44a677b..2c56b17e 100644
--- a/gear-programs/historical-proxy/app/src/lib.rs
+++ b/gear-programs/historical-proxy/app/src/lib.rs
@@ -18,7 +18,6 @@ pub struct HistoricalProxyProgram(RefCell<state::ProxyState>);
 
 #[sails_rs::program]
 impl HistoricalProxyProgram {
-    // Program's constructor
     #[allow(clippy::new_without_default)]
     pub fn new() -> Self {
         let exec_context = GStdExecContext::new();
@@ -28,7 +27,6 @@ impl HistoricalProxyProgram {
         }))
     }
 
-    // Exposed service
     pub fn historical_proxy(&self) -> service::HistoricalProxyService<GStdExecContext> {
         service::HistoricalProxyService::new(&self.0, GStdExecContext::new())
     }
diff --git a/gear-programs/historical-proxy/app/src/state.rs b/gear-programs/historical-proxy/app/src/state.rs
index 7deb1d28..d4cbf6cf 100644
--- a/gear-programs/historical-proxy/app/src/state.rs
+++ b/gear-programs/historical-proxy/app/src/state.rs
@@ -1,25 +1,30 @@
 use super::error::ProxyError;
 use super::{ActorId, Vec};
+
 pub type Slot = u64;
 
+/// State of the Historical Proxy service.
 pub struct ProxyState {
     pub admin: ActorId,
     pub endpoints: EndpointList,
 }
 
+/// Mapping between endpoints and Ethereum slots they're active from.
+///
+/// ### Invariant
+///
+/// Endpoints are stored in ascending order, sorted by slot number.
+#[derive(Default)]
 pub struct EndpointList(Vec<(Slot, ActorId)>);
 
-impl Default for EndpointList {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
 impl EndpointList {
     pub fn new() -> Self {
         Self(Vec::with_capacity(2))
     }
 
+    /// Add new endpoint that will be active starting from `slot`(inclusive).
+    ///
+    /// Panics if provided `slot` <= greatest already existing slot.
     pub fn push(&mut self, slot: Slot, actor_id: ActorId) {
         assert!(
             self.0.is_empty() || self.0[self.0.len() - 1].0 < slot,
@@ -28,10 +33,14 @@ impl EndpointList {
         self.0.push((slot, actor_id));
     }
 
+    /// Get list of currently active endpoints. Returns `Vec<(Slot, ActorId)>`
+    /// where `ActorId` means endpoint address and `Slot` means Ethereum slot
+    /// this endpoint is active from(inclusive).
     pub fn endpoints(&self) -> Vec<(Slot, ActorId)> {
         self.0.clone()
     }
 
+    /// Get endpoint for the specified slot. Will return error if endpoint is not found.
     pub fn endpoint_for(&self, slot: Slot) -> Result<ActorId, ProxyError> {
         match self.0.binary_search_by(|(s, _)| s.cmp(&slot)) {
             Ok(i) => Ok(self.0[i].1),