diff --git a/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistry.java b/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistry.java
index 29f8c330e1..712a7f35a5 100644
--- a/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistry.java
+++ b/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistry.java
@@ -16,7 +16,7 @@
 
 package org.springframework.web.service.registry;
 
-import org.jspecify.annotations.Nullable;
+import java.util.Set;
 
 /**
  * A registry that contains HTTP Service client proxies.
@@ -35,18 +35,34 @@ public interface HttpServiceProxyRegistry {
 	 * @param httpServiceType the type of client proxy
 	 * @return the proxy, or {@code null} if not found
 	 * @param <P> the type of HTTP Interface client proxy
-	 * @throws IllegalArgumentException if more than one client proxy of the
+	 * @throws IllegalArgumentException if there is no client proxy of the given
+	 * type, or there is more than one client proxy of the given type.
 	 * given type exists across groups
 	 */
-	<P> @Nullable P getClient(Class<P> httpServiceType);
+	<P> P getClient(Class<P> httpServiceType);
 
 	/**
 	 * Return an HTTP service client proxy from the given group.
 	 * @param groupName the name of the group
 	 * @param httpServiceType the type of client proxy
 	 * @return the proxy, or {@code null} if not found
+	 * @throws IllegalArgumentException if there is no group with the given
+	 * name, or no client proxy of the given type in the group.
 	 * @param <P> the type of HTTP Interface client proxy
 	 */
-	<P> @Nullable P getClient(String groupName, Class<P> httpServiceType);
+	<P> P getClient(String groupName, Class<P> httpServiceType);
+
+	/**
+	 * Return the names of all groups in the registry.
+	 */
+	Set<String> getGroupNames();
+
+	/**
+	 * Return the HTTP service types for all client proxies in the given group.
+	 * @param groupName the name of the group
+	 * @return the HTTP service types
+	 * @throws IllegalArgumentException if there is no group with the given name.
+	 */
+	Set<Class<?>> getClientTypesInGroup(String groupName);
 
 }
diff --git a/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistryFactoryBean.java b/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistryFactoryBean.java
index b890f4d4c7..fcfc13f40a 100644
--- a/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistryFactoryBean.java
+++ b/spring-web/src/main/java/org/springframework/web/service/registry/HttpServiceProxyRegistryFactoryBean.java
@@ -278,16 +278,36 @@ public final class HttpServiceProxyRegistryFactoryBean
 
 		@SuppressWarnings("unchecked")
 		@Override
-		public <P> @Nullable P getClient(Class<P> type) {
-			List<Object> proxies = this.directLookupMap.getOrDefault(type, Collections.emptyList());
-			Assert.state(proxies.size() <= 1, "No unique client of type " + type.getName());
-			return (!proxies.isEmpty() ? (P) proxies.get(0) : null);
+		public <P> P getClient(Class<P> type) {
+			List<Object> map = this.directLookupMap.getOrDefault(type, Collections.emptyList());
+			Assert.notEmpty(map, "No client of type " + type.getName());
+			Assert.isTrue(map.size() <= 1, "No unique client of type " + type.getName());
+			return (P) map.get(0);
 		}
 
 		@SuppressWarnings("unchecked")
 		@Override
-		public <P> @Nullable P getClient(String groupName, Class<P> httpServiceType) {
-			return (P) this.groupProxyMap.getOrDefault(groupName, Collections.emptyMap()).get(httpServiceType);
+		public <P> P getClient(String groupName, Class<P> type) {
+			Map<Class<?>, Object> map = getProxyMapForGroup(groupName);
+			P proxy = (P) map.get(type);
+			Assert.notNull(proxy, "No client of type " + type + " in group '" + groupName + "': " + map.keySet());
+			return proxy;
+		}
+
+		@Override
+		public Set<String> getGroupNames() {
+			return this.groupProxyMap.keySet();
+		}
+
+		@Override
+		public Set<Class<?>> getClientTypesInGroup(String groupName) {
+			return getProxyMapForGroup(groupName).keySet();
+		}
+
+		private Map<Class<?>, Object> getProxyMapForGroup(String groupName) {
+			Map<Class<?>, Object> map = this.groupProxyMap.get(groupName);
+			Assert.notNull(map, "No group with name '" + groupName + "'");
+			return map;
 		}
 	}