diff --git a/src/core/border_router/routing_manager.cpp b/src/core/border_router/routing_manager.cpp
index 1a7d2e8f2..443e81854 100644
--- a/src/core/border_router/routing_manager.cpp
+++ b/src/core/border_router/routing_manager.cpp
@@ -1022,7 +1022,7 @@ void RoutingManager::HandleRouterAdvertisement(const Ip6::Address &aSrcAddress,
 
             if (pio->IsValid())
             {
-                needReevaluate |= UpdateDiscoveredPrefixes(*pio);
+                needReevaluate |= UpdateDiscoveredOnLinkPrefix(*pio);
             }
         }
         break;
@@ -1033,7 +1033,7 @@ void RoutingManager::HandleRouterAdvertisement(const Ip6::Address &aSrcAddress,
 
             if (rio->IsValid())
             {
-                needReevaluate |= UpdateDiscoveredPrefixes(*rio);
+                UpdateDiscoveredOmrPrefix(*rio);
             }
         }
         break;
@@ -1059,7 +1059,10 @@ exit:
     return;
 }
 
-bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::PrefixInfoOption &aPio)
+// Adds or deprecates a discovered on-link prefix (new external routes may be added
+// to the Thread network). Returns a boolean which indicates whether we need to do
+// routing policy evaluation.
+bool RoutingManager::UpdateDiscoveredOnLinkPrefix(const RouterAdv::PrefixInfoOption &aPio)
 {
     Ip6::Prefix     prefix         = aPio.GetPrefix();
     bool            needReevaluate = false;
@@ -1153,10 +1156,11 @@ exit:
     return needReevaluate;
 }
 
-bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::RouteInfoOption &aRio)
+// Adds or removes a discovered OMR prefix (external route will be added to or removed
+// from the Thread network).
+void RoutingManager::UpdateDiscoveredOmrPrefix(const RouterAdv::RouteInfoOption &aRio)
 {
-    Ip6::Prefix     prefix         = aRio.GetPrefix();
-    bool            needReevaluate = false;
+    Ip6::Prefix     prefix = aRio.GetPrefix();
     ExternalPrefix  omrPrefix;
     ExternalPrefix *existingPrefix = nullptr;
 
@@ -1184,7 +1188,7 @@ bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::RouteInfoOption &
 
     if (aRio.GetRouteLifetime() == 0)
     {
-        needReevaluate = InvalidateDiscoveredPrefixes(&prefix, /* aIsOnLinkPrefix */ false);
+        InvalidateDiscoveredPrefixes(&prefix, /* aIsOnLinkPrefix */ false);
         ExitNow();
     }
 
@@ -1215,7 +1219,6 @@ bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::RouteInfoOption &
         {
             SuccessOrExit(AddExternalRoute(prefix, omrPrefix.mRoutePreference));
             existingPrefix = mDiscoveredPrefixes.PushBack();
-            needReevaluate = true;
         }
         else
         {
@@ -1230,12 +1233,11 @@ bool RoutingManager::UpdateDiscoveredPrefixes(const RouterAdv::RouteInfoOption &
     mDiscoveredPrefixStaleTimer.FireAtIfEarlier(existingPrefix->GetStaleTime());
 
 exit:
-    return needReevaluate;
+    return;
 }
 
-bool RoutingManager::InvalidateDiscoveredPrefixes(const Ip6::Prefix *aPrefix, bool aIsOnLinkPrefix)
+void RoutingManager::InvalidateDiscoveredPrefixes(const Ip6::Prefix *aPrefix, bool aIsOnLinkPrefix)
 {
-    bool                didRemove                = false;
     TimeMilli           now                      = TimerMilli::GetNow();
     uint8_t             remainingOnLinkPrefixNum = 0;
     ExternalPrefixArray remainingPrefixes;
@@ -1248,7 +1250,6 @@ bool RoutingManager::InvalidateDiscoveredPrefixes(const Ip6::Prefix *aPrefix, bo
             (prefix.GetExpireTime() <= now))
         {
             RemoveExternalRoute(prefix.mPrefix);
-            didRemove = true;
         }
         else
         {
@@ -1271,8 +1272,6 @@ bool RoutingManager::InvalidateDiscoveredPrefixes(const Ip6::Prefix *aPrefix, bo
         // To discover more on-link prefixes or timeout to advertise my local on-link prefix.
         StartRouterSolicitationDelay();
     }
-
-    return didRemove; // If anything was removed we need to reevaluate.
 }
 
 void RoutingManager::InvalidateAllDiscoveredPrefixes(void)
diff --git a/src/core/border_router/routing_manager.hpp b/src/core/border_router/routing_manager.hpp
index ec60fdd6b..ab383b6da 100644
--- a/src/core/border_router/routing_manager.hpp
+++ b/src/core/border_router/routing_manager.hpp
@@ -307,9 +307,9 @@ private:
     void DeprecateOnLinkPrefix(void);
     void HandleRouterSolicit(const Ip6::Address &aSrcAddress, const uint8_t *aBuffer, uint16_t aBufferLength);
     void HandleRouterAdvertisement(const Ip6::Address &aSrcAddress, const uint8_t *aBuffer, uint16_t aBufferLength);
-    bool UpdateDiscoveredPrefixes(const RouterAdv::PrefixInfoOption &aPio);
-    bool UpdateDiscoveredPrefixes(const RouterAdv::RouteInfoOption &aRio);
-    bool InvalidateDiscoveredPrefixes(const Ip6::Prefix *aPrefix = nullptr, bool aIsOnLinkPrefix = true);
+    bool UpdateDiscoveredOnLinkPrefix(const RouterAdv::PrefixInfoOption &aPio);
+    void UpdateDiscoveredOmrPrefix(const RouterAdv::RouteInfoOption &aRio);
+    void InvalidateDiscoveredPrefixes(const Ip6::Prefix *aPrefix = nullptr, bool aIsOnLinkPrefix = true);
     void InvalidateAllDiscoveredPrefixes(void);
     bool NetworkDataContainsOmrPrefix(const Ip6::Prefix &aPrefix) const;
     bool UpdateRouterAdvMessage(const RouterAdv::RouterAdvMessage *aRouterAdvMessage);