diff --git a/aws/smithy-aws-traits/src/main/java/software/amazon/smithy/aws/traits/clientendpointdiscovery/ClientEndpointDiscoveryValidator.java b/aws/smithy-aws-traits/src/main/java/software/amazon/smithy/aws/traits/clientendpointdiscovery/ClientEndpointDiscoveryValidator.java
index 3c2951856c2..979feff7dc5 100644
--- a/aws/smithy-aws-traits/src/main/java/software/amazon/smithy/aws/traits/clientendpointdiscovery/ClientEndpointDiscoveryValidator.java
+++ b/aws/smithy-aws-traits/src/main/java/software/amazon/smithy/aws/traits/clientendpointdiscovery/ClientEndpointDiscoveryValidator.java
@@ -38,6 +38,8 @@
 import software.amazon.smithy.utils.SetUtils;
 
 public class ClientEndpointDiscoveryValidator extends AbstractValidator {
+    private static final Set<String> VALID_INPUT_MEMBERS = SetUtils.of("Operation", "Identifiers");
+
     @Override
     public List<ValidationEvent> validate(Model model) {
         ClientEndpointDiscoveryIndex discoveryIndex = model.getKnowledge(ClientEndpointDiscoveryIndex.class);
@@ -133,37 +135,9 @@ private List<ValidationEvent> validateEndpointOperation(
             Model model, OperationIndex opIndex, OperationShape operation
     ) {
         List<ValidationEvent> events = new ArrayList<>();
-        opIndex.getInput(operation).ifPresent(input -> {
-            Set<String> memberNames = SetUtils.copyOf(input.getMemberNames());
-            if (!memberNames.equals(SetUtils.of("Operation", "Identifiers"))) {
-                events.add(error(input, String.format(
-                        "Input for endpoint discovery operation `%s` may only have the members Operation and "
-                                + "Identifiers but found: %s",
-                        operation.getId().toString(),
-                        String.join(", ", memberNames)
-                )));
-            }
-
-            input.getMember("Operation")
-                    .flatMap(member -> model.getShape(member.getTarget()))
-                    .filter(shape -> !shape.isStringShape())
-                    .ifPresent(shape -> events.add(error(
-                            shape, "The Operation member of an endpoint discovery operation must be a string")));
-
-            input.getMember("Identifiers")
-                    .map(member -> Pair.of(member, model.getShape(member.getTarget())))
-                    .ifPresent(pair -> {
-                        Optional<MapShape> map = pair.getRight().flatMap(Shape::asMapShape);
-                        if (map.isPresent()) {
-                            Optional<Shape> value = model.getShape(map.get().getValue().getTarget());
-                            if (value.isPresent() && value.get().isStringShape()) {
-                                return;
-                            }
-                        }
-                        events.add(error(pair.getLeft(), "The Identifiers member of an endpoint discovery "
-                                + "operation must be a map whose keys and values are strings."));
-                    });
-        });
+        opIndex.getInput(operation)
+                .map(input -> validateEndpointOperationInput(model, input, operation))
+                .ifPresent(events::addAll);
 
         Optional<StructureShape> output = opIndex.getOutput(operation);
         if (!output.isPresent()) {
@@ -224,4 +198,40 @@ private List<ValidationEvent> validateEndpointOperation(
 
         return events;
     }
+
+    private List<ValidationEvent> validateEndpointOperationInput(
+            Model model, StructureShape input, OperationShape operation
+    ) {
+        List<ValidationEvent> events = new ArrayList<>();
+        Set<String> memberNames = SetUtils.copyOf(input.getMemberNames());
+        if (!VALID_INPUT_MEMBERS.containsAll(memberNames)) {
+            events.add(error(input, String.format(
+                    "Input for endpoint discovery operation `%s` may only have the members Operation and "
+                            + "Identifiers but found: %s",
+                    operation.getId().toString(),
+                    String.join(", ", memberNames)
+            )));
+        }
+
+        input.getMember("Operation")
+                .flatMap(member -> model.getShape(member.getTarget()))
+                .filter(shape -> !shape.isStringShape())
+                .ifPresent(shape -> events.add(error(
+                        shape, "The Operation member of an endpoint discovery operation must be a string")));
+
+        input.getMember("Identifiers")
+                .map(member -> Pair.of(member, model.getShape(member.getTarget())))
+                .ifPresent(pair -> {
+                    Optional<MapShape> map = pair.getRight().flatMap(Shape::asMapShape);
+                    if (map.isPresent()) {
+                        Optional<Shape> value = model.getShape(map.get().getValue().getTarget());
+                        if (value.isPresent() && value.get().isStringShape()) {
+                            return;
+                        }
+                    }
+                    events.add(error(pair.getLeft(), "The Identifiers member of an endpoint discovery "
+                            + "operation must be a map whose keys and values are strings."));
+                });
+        return events;
+    }
 }
diff --git a/aws/smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/clientendpointdiscovery/errorfiles/no-input.errors b/aws/smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/clientendpointdiscovery/errorfiles/no-input.errors
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/aws/smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/clientendpointdiscovery/errorfiles/no-input.json b/aws/smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/clientendpointdiscovery/errorfiles/no-input.json
new file mode 100644
index 00000000000..f025f2f3905
--- /dev/null
+++ b/aws/smithy-aws-traits/src/test/resources/software/amazon/smithy/aws/traits/clientendpointdiscovery/errorfiles/no-input.json
@@ -0,0 +1,111 @@
+{
+    "smithy": "0.4.0",
+    "ns.foo": {
+        "shapes": {
+            "FooService": {
+                "type": "service",
+                "version": "2019-09-10",
+                "aws.api#clientEndpointDiscovery": {
+                    "operation": "ns.foo#DescribeEndpoints",
+                    "error": "ns.foo#InvalidEndpointError"
+                },
+                "operations": [
+                    "DescribeEndpoints",
+                    "GetObject",
+                    "PutObject"
+                ]
+            },
+            "BarService": {
+                "type": "service",
+                "version": "2019-09-10",
+                "operations": [
+                    "DescribeEndpoints"
+                ]
+            },
+            "DescribeEndpoints": {
+                "type": "operation",
+                "input": "DescribeEndpointsInput",
+                "output": "DescribeEndpointsOutput"
+            },
+            "DescribeEndpointsInput": {
+                "type": "structure"
+            },
+            "DescribeEndpointsOutput": {
+                "type": "structure",
+                "members": {
+                    "Endpoints": {
+                        "target": "Endpoints"
+                    }
+                }
+            },
+            "Endpoints": {
+                "type": "list",
+                "member": {
+                    "target": "Endpoint"
+                }
+            },
+            "Endpoint": {
+                "type": "structure",
+                "members": {
+                    "Address": {
+                        "target": "smithy.api#String"
+                    },
+                    "CachePeriodInMinutes": {
+                        "target": "smithy.api#Long"
+                    }
+                }
+            },
+            "GetObject": {
+                "type": "operation",
+                "input": "GetObjectInput",
+                "output": "GetObjectOutput",
+                "aws.api#clientDiscoveredEndpoint": {
+                    "required": true
+                },
+                "errors": ["InvalidEndpointError"]
+            },
+            "GetObjectInput": {
+                "type": "structure",
+                "members": {
+                    "Id": {
+                        "target": "smithy.api#String",
+                        "required": true
+                    }
+                }
+            },
+            "GetObjectOutput": {
+                "type": "structure",
+                "members": {
+                    "Object": {
+                        "target": "smithy.api#Blob"
+                    }
+                }
+            },
+            "PutObject": {
+                "type": "operation",
+                "input": "PutObjectInput",
+                "aws.api#clientDiscoveredEndpoint": {
+                    "required": false
+                },
+                "errors": ["InvalidEndpointError"]
+            },
+            "PutObjectInput": {
+                "type": "structure",
+                "members": {
+                    "Id": {
+                        "target": "smithy.api#String",
+                        "required": true
+                    },
+                    "Object": {
+                        "target": "smithy.api#Blob"
+                    }
+                }
+            },
+            "InvalidEndpointError": {
+                "type": "structure",
+                "error": "client",
+                "httpError": 421
+            }
+        }
+    }
+}
\ No newline at end of file