diff --git a/packages/grpc-native-core/ext/call.cc b/packages/grpc-native-core/ext/call.cc
index 8922bc66..25370759 100644
--- a/packages/grpc-native-core/ext/call.cc
+++ b/packages/grpc-native-core/ext/call.cc
@@ -81,8 +81,13 @@ Local<Value> nanErrorWithCode(const char *msg, grpc_call_error code) {
   return scope.Escape(err);
 }
 
-bool CreateMetadataArray(Local<Object> metadata, grpc_metadata_array *array) {
+bool CreateMetadataArray(Local<Object> metadata_obj, grpc_metadata_array *array) {
   HandleScope scope;
+  Local<Value> metadata_value = (Nan::Get(metadata_obj, Nan::New("metadata").ToLocalChecked())).ToLocalChecked();
+  if (!metadata_value->IsObject()) {
+    return false;
+  }
+  Local<Object> metadata = Nan::To<Object>(metadata_value).ToLocalChecked();
   Local<Array> keys = Nan::GetOwnPropertyNames(metadata).ToLocalChecked();
   for (unsigned int i = 0; i < keys->Length(); i++) {
     Local<String> current_key =
@@ -159,7 +164,10 @@ Local<Value> ParseMetadata(const grpc_metadata_array *metadata_array) {
       Nan::Set(array, array->Length(), CopyStringFromSlice(elem->value));
     }
   }
-  return scope.Escape(metadata_object);
+  Local<Object> result = Nan::New<Object>();
+  Nan::Set(result, Nan::New("metadata").ToLocalChecked(), metadata_object);
+  Nan::Set(result, Nan::New("flags").ToLocalChecked(), Nan::New<v8::Uint32>(0));
+  return scope.Escape(result);
 }
 
 Local<Value> Op::GetOpType() const {
@@ -185,7 +193,17 @@ class SendMetadataOp : public Op {
     if (maybe_metadata.IsEmpty()) {
       return false;
     }
-    if (!CreateMetadataArray(maybe_metadata.ToLocalChecked(), &send_metadata)) {
+    Local<Object> metadata_object = maybe_metadata.ToLocalChecked();
+    MaybeLocal<Value> maybe_flag_value =
+        Nan::Get(metadata_object, Nan::New("flags").ToLocalChecked());
+    if (!maybe_flag_value.IsEmpty()) {
+      Local<Value> flag_value = maybe_flag_value.ToLocalChecked();
+      if (flag_value->IsUint32()) {
+        Maybe<uint32_t> maybe_flag = Nan::To<uint32_t>(flag_value);
+        out->flags |= maybe_flag.FromMaybe(0) & GRPC_INITIAL_METADATA_USED_MASK;
+      }
+    }
+    if (!CreateMetadataArray(metadata_object, &send_metadata)) {
       return false;
     }
     out->data.send_initial_metadata.count = send_metadata.count;
@@ -225,7 +243,7 @@ class SendMessageOp : public Op {
       Local<Value> flag_value = maybe_flag_value.ToLocalChecked();
       if (flag_value->IsUint32()) {
         Maybe<uint32_t> maybe_flag = Nan::To<uint32_t>(flag_value);
-        out->flags = maybe_flag.FromMaybe(0) & GRPC_WRITE_USED_MASK;
+        out->flags |= maybe_flag.FromMaybe(0) & GRPC_WRITE_USED_MASK;
       }
     }
     send_message = BufferToByteBuffer(value);
diff --git a/packages/grpc-native-core/index.d.ts b/packages/grpc-native-core/index.d.ts
index 808051d0..17790654 100644
--- a/packages/grpc-native-core/index.d.ts
+++ b/packages/grpc-native-core/index.d.ts
@@ -489,10 +489,29 @@ declare module "grpc" {
   type sendUnaryData<ResponseType> =
     (error: ServiceError | null, value: ResponseType | null, trailer?: Metadata, flags?: number) => void;
 
+  interface MetadataOptions {
+    /* Signal that the request is idempotent. Defaults to false */
+    idempotentRequest?: boolean;
+    /* Signal that the call should not return UNAVAILABLE before it has
+     * started. Defaults to true. */
+    waitForReady?: boolean;
+    /* Signal that the call is cacheable. GRPC is free to use GET verb.
+     * Defaults to false */
+    cacheableRequest?: boolean;
+    /* Signal that the initial metadata should be corked. Defaults to false. */
+    corked?: boolean;
+  }
+
   /**
    * A class for storing metadata. Keys are normalized to lowercase ASCII.
    */
   export class Metadata {
+    /**
+     * @param options Boolean options for the beginning of the call.
+     *   These options only have any effect when passed at the beginning of
+     *   a client request.
+     */
+    constructor(options?: MetadataOptions);
     /**
      * Sets the given value for the given key by replacing any other values
      * associated with that key. Normalizes the key.
@@ -536,6 +555,14 @@ declare module "grpc" {
      * @return The newly cloned object.
      */
     clone(): Metadata;
+
+    /**
+     * Set options on the metadata object
+     * @param options Boolean options for the beginning of the call.
+     *   These options only have any effect when passed at the beginning of
+     *   a client request.
+     */
+    setOptions(options: MetadataOptions);
   }
 
   export type MetadataValue = string | Buffer;
diff --git a/packages/grpc-native-core/src/metadata.js b/packages/grpc-native-core/src/metadata.js
index 31c6329e..ee442953 100644
--- a/packages/grpc-native-core/src/metadata.js
+++ b/packages/grpc-native-core/src/metadata.js
@@ -22,18 +22,36 @@ var clone = require('lodash.clone');
 
 var grpc = require('./grpc_extension');
 
+const IDEMPOTENT_REQUEST_FLAG = 0x10;
+const WAIT_FOR_READY_FLAG = 0x20;
+const CACHEABLE_REQUEST_FLAG = 0x40;
+const WAIT_FOR_READY_EXPLICITLY_SET_FLAG = 0x80;
+const CORKED_FLAG = 0x100;
+
 /**
  * Class for storing metadata. Keys are normalized to lowercase ASCII.
  * @memberof grpc
  * @constructor
+ * @param {Object=} options Boolean options for the beginning of the call.
+ *     These options only have any effect when passed at the beginning of
+ *     a client request.
+ * @param {boolean=} [options.idempotentRequest=false] Signal that the request
+ *     is idempotent
+ * @param {boolean=} [options.waitForReady=true] Signal that the call should
+ *     not return UNAVAILABLE before it has started.
+ * @param {boolean=} [options.cacheableRequest=false] Signal that the call is
+ *     cacheable. GRPC is free to use GET verb.
+ * @param {boolean=} [options.corked=false] Signal that the initial metadata
+ *     should be corked.
  * @example
  * var metadata = new metadata_module.Metadata();
  * metadata.set('key1', 'value1');
  * metadata.add('key1', 'value2');
  * metadata.get('key1') // returns ['value1', 'value2']
  */
-function Metadata() {
+function Metadata(options) {
   this._internal_repr = {};
+  this.setOptions(options);
 }
 
 function normalizeKey(key) {
@@ -141,34 +159,82 @@ Metadata.prototype.clone = function() {
     const value = this._internal_repr[key];
     copy._internal_repr[key] = clone(value);
   });
+  copy.flags = this.flags;
   return copy;
 };
 
+/**
+ * Set options on the metadata object
+ * @param {Object} options Boolean options for the beginning of the call.
+ *     These options only have any effect when passed at the beginning of
+ *     a client request.
+ * @param {boolean=} [options.idempotentRequest=false] Signal that the request
+ *     is idempotent
+ * @param {boolean=} [options.waitForReady=true] Signal that the call should
+ *     not return UNAVAILABLE before it has started.
+ * @param {boolean=} [options.cacheableRequest=false] Signal that the call is
+ *     cacheable. GRPC is free to use GET verb.
+ * @param {boolean=} [options.corked=false] Signal that the initial metadata
+ *     should be corked.
+ */
+Metadata.prototype.setOptions = function(options) {
+  let flags = 0;
+  if (options) {
+    if (options.idempotentRequest) {
+      flags |= IDEMPOTENT_REQUEST_FLAG;
+    }
+    if (options.hasOwnProperty('waitForReady')) {
+      flags |= WAIT_FOR_READY_EXPLICITLY_SET_FLAG;
+      if (options.waitForReady) {
+        flags |= WAIT_FOR_READY_FLAG;
+      }
+    }
+    if (options.cacheableRequest) {
+      flags |= CACHEABLE_REQUEST_FLAG;
+    }
+    if (options.corked) {
+      flags |= CORKED_FLAG;
+    }
+  }
+  this.flags = flags;
+}
+
+/**
+ * Metadata representation as passed to and the native addon
+ * @typedef {object} grpc~CoreMetadata
+ * @param {Object.<String, Array.<String|Buffer>>} metadata The metadata
+ * @param {number} flags Metadata flags
+ */
+
 /**
  * Gets the metadata in the format used by interal code. Intended for internal
  * use only. API stability is not guaranteed.
  * @private
- * @return {Object.<String, Array.<String|Buffer>>} The metadata
+ * @return {grpc~CoreMetadata} The metadata
  */
 Metadata.prototype._getCoreRepresentation = function() {
-  return this._internal_repr;
+  return {
+    metadata: this._internal_repr,
+    flags: this.flags
+  };
 };
 
 /**
  * Creates a Metadata object from a metadata map in the internal format.
  * Intended for internal use only. API stability is not guaranteed.
  * @private
- * @param {Object.<String, Array.<String|Buffer>>} The metadata
+ * @param {grpc~CoreMetadata} metadata The metadata object from core
  * @return {Metadata} The new Metadata object
  */
 Metadata._fromCoreRepresentation = function(metadata) {
   var newMetadata = new Metadata();
   if (metadata) {
-    Object.keys(metadata).forEach(key => {
-      const value = metadata[key];
+    Object.keys(metadata.metadata).forEach(key => {
+      const value = metadata.metadata[key];
       newMetadata._internal_repr[key] = clone(value);
     });
   }
+  newMetadata.flags = metadata.flags;
   return newMetadata;
 };
 
diff --git a/packages/grpc-native-core/test/call_test.js b/packages/grpc-native-core/test/call_test.js
index bba4cce0..42fd3d01 100644
--- a/packages/grpc-native-core/test/call_test.js
+++ b/packages/grpc-native-core/test/call_test.js
@@ -128,8 +128,9 @@ describe('call', function() {
       var call = channel.createCall('method', getDeadline(1));
       assert.doesNotThrow(function() {
         var batch = {};
-        batch[grpc.opType.SEND_INITIAL_METADATA] = {'key1': ['value1'],
-                                                    'key2': ['value2']};
+        batch[grpc.opType.SEND_INITIAL_METADATA] = {
+          metadata: {'key1': ['value1'], 'key2': ['value2']}
+        };
         call.startBatch(batch, function(err, resp) {
           assert.ifError(err);
           assert.deepEqual(resp, {'send_metadata': true});
@@ -142,8 +143,10 @@ describe('call', function() {
       assert.doesNotThrow(function() {
         var batch = {};
         batch[grpc.opType.SEND_INITIAL_METADATA] = {
-          'key1-bin': [Buffer.from('value1')],
-          'key2-bin': [Buffer.from('value2')]
+          metadata: {
+            'key1-bin': [Buffer.from('value1')],
+            'key2-bin': [Buffer.from('value2')]
+          }
         };
         call.startBatch(batch, function(err, resp) {
           assert.ifError(err);
@@ -174,6 +177,11 @@ describe('call', function() {
         batch[grpc.opType.SEND_INITIAL_METADATA] = 5;
         call.startBatch(batch, function(){});
       }, TypeError);
+      assert.throws(function() {
+        var batch = {};
+        batch[grpc.opType.SEND_INITIAL_METADATA] = {};
+        call.startBatch(batch, function(){});
+      }, TypeError);
     });
   });
   describe('startBatch with message', function() {
diff --git a/packages/grpc-native-core/test/end_to_end_test.js b/packages/grpc-native-core/test/end_to_end_test.js
index da6fac6c..ae165b14 100644
--- a/packages/grpc-native-core/test/end_to_end_test.js
+++ b/packages/grpc-native-core/test/end_to_end_test.js
@@ -65,7 +65,7 @@ describe('end-to-end', function() {
                              'dummy_method',
                              Infinity);
     var client_batch = {};
-    client_batch[grpc.opType.SEND_INITIAL_METADATA] = {};
+    client_batch[grpc.opType.SEND_INITIAL_METADATA] = {metadata: {}};
     client_batch[grpc.opType.SEND_CLOSE_FROM_CLIENT] = true;
     client_batch[grpc.opType.RECV_INITIAL_METADATA] = true;
     client_batch[grpc.opType.RECV_STATUS_ON_CLIENT] = true;
@@ -74,11 +74,17 @@ describe('end-to-end', function() {
       assert.deepEqual(response, {
         send_metadata: true,
         client_close: true,
-        metadata: {},
+        metadata: {
+          metadata: {},
+          flags: 0
+        },
         status: {
           code: constants.status.OK,
           details: status_text,
-          metadata: {}
+          metadata: {
+            metadata: {},
+            flags: 0
+          }
         }
       });
       done();
@@ -90,9 +96,9 @@ describe('end-to-end', function() {
       var server_call = new_call.call;
       assert.notEqual(server_call, null);
       var server_batch = {};
-      server_batch[grpc.opType.SEND_INITIAL_METADATA] = {};
+      server_batch[grpc.opType.SEND_INITIAL_METADATA] = {metadata: {}};
       server_batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
-        metadata: {},
+        metadata: {metadata: {}},
         code: constants.status.OK,
         details: status_text
       };
@@ -116,7 +122,9 @@ describe('end-to-end', function() {
                              Infinity);
     var client_batch = {};
     client_batch[grpc.opType.SEND_INITIAL_METADATA] = {
-      client_key: ['client_value']
+      metadata: {
+        client_key: ['client_value']
+      }
     };
     client_batch[grpc.opType.SEND_CLOSE_FROM_CLIENT] = true;
     client_batch[grpc.opType.RECV_INITIAL_METADATA] = true;
@@ -126,10 +134,13 @@ describe('end-to-end', function() {
       assert.deepEqual(response,{
         send_metadata: true,
         client_close: true,
-        metadata: {server_key: ['server_value']},
+        metadata: {metadata: {
+          server_key: ['server_value']}, 
+          flags: 0
+        },
         status: {code: constants.status.OK,
                  details: status_text,
-                 metadata: {}}
+                 metadata: {metadata: {}, flags: 0}}
       });
       done();
     });
@@ -137,16 +148,18 @@ describe('end-to-end', function() {
     server.requestCall(function(err, call_details) {
       var new_call = call_details.new_call;
       assert.notEqual(new_call, null);
-      assert.strictEqual(new_call.metadata.client_key[0],
+      assert.strictEqual(new_call.metadata.metadata.client_key[0],
                          'client_value');
       var server_call = new_call.call;
       assert.notEqual(server_call, null);
       var server_batch = {};
       server_batch[grpc.opType.SEND_INITIAL_METADATA] = {
-        server_key: ['server_value']
+        metadata: {
+          server_key: ['server_value']
+        }
       };
       server_batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
-        metadata: {},
+        metadata: {metadata: {}},
         code: constants.status.OK,
         details: status_text
       };
@@ -171,7 +184,7 @@ describe('end-to-end', function() {
                              'dummy_method',
                              Infinity);
     var client_batch = {};
-    client_batch[grpc.opType.SEND_INITIAL_METADATA] = {};
+    client_batch[grpc.opType.SEND_INITIAL_METADATA] = {metadata: {}};
     client_batch[grpc.opType.SEND_MESSAGE] = Buffer.from(req_text);
     client_batch[grpc.opType.SEND_CLOSE_FROM_CLIENT] = true;
     client_batch[grpc.opType.RECV_INITIAL_METADATA] = true;
@@ -181,12 +194,12 @@ describe('end-to-end', function() {
       assert.ifError(err);
       assert(response.send_metadata);
       assert(response.client_close);
-      assert.deepEqual(response.metadata, {});
+      assert.deepEqual(response.metadata, {metadata: {}, flags: 0});
       assert(response.send_message);
       assert.strictEqual(response.read.toString(), reply_text);
       assert.deepEqual(response.status, {code: constants.status.OK,
                                          details: status_text,
-                                         metadata: {}});
+                                         metadata: {metadata: {}, flags: 0}});
       done();
     });
 
@@ -196,7 +209,7 @@ describe('end-to-end', function() {
       var server_call = new_call.call;
       assert.notEqual(server_call, null);
       var server_batch = {};
-      server_batch[grpc.opType.SEND_INITIAL_METADATA] = {};
+      server_batch[grpc.opType.SEND_INITIAL_METADATA] = {metadata: {}};
       server_batch[grpc.opType.RECV_MESSAGE] = true;
       server_call.startBatch(server_batch, function(err, response) {
         assert.ifError(err);
@@ -205,7 +218,7 @@ describe('end-to-end', function() {
         var response_batch = {};
         response_batch[grpc.opType.SEND_MESSAGE] = Buffer.from(reply_text);
         response_batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
-          metadata: {},
+          metadata: {metadata: {}},
           code: constants.status.OK,
           details: status_text
         };
@@ -226,7 +239,7 @@ describe('end-to-end', function() {
                              'dummy_method',
                              Infinity);
     var client_batch = {};
-    client_batch[grpc.opType.SEND_INITIAL_METADATA] = {};
+    client_batch[grpc.opType.SEND_INITIAL_METADATA] = {metadata: {}};
     client_batch[grpc.opType.SEND_MESSAGE] = Buffer.from(requests[0]);
     client_batch[grpc.opType.RECV_INITIAL_METADATA] = true;
     call.startBatch(client_batch, function(err, response) {
@@ -234,7 +247,7 @@ describe('end-to-end', function() {
       assert.deepEqual(response, {
         send_metadata: true,
         send_message: true,
-        metadata: {}
+        metadata: {metadata: {}, flags: 0}
       });
       var req2_batch = {};
       req2_batch[grpc.opType.SEND_MESSAGE] = Buffer.from(requests[1]);
@@ -248,7 +261,7 @@ describe('end-to-end', function() {
           status: {
             code: constants.status.OK,
             details: status_text,
-            metadata: {}
+            metadata: {metadata: {}, flags: 0}
           }
         });
         done();
@@ -261,7 +274,7 @@ describe('end-to-end', function() {
       var server_call = new_call.call;
       assert.notEqual(server_call, null);
       var server_batch = {};
-      server_batch[grpc.opType.SEND_INITIAL_METADATA] = {};
+      server_batch[grpc.opType.SEND_INITIAL_METADATA] = {metadata: {}};
       server_batch[grpc.opType.RECV_MESSAGE] = true;
       server_call.startBatch(server_batch, function(err, response) {
         assert.ifError(err);
@@ -275,7 +288,7 @@ describe('end-to-end', function() {
           var end_batch = {};
           end_batch[grpc.opType.RECV_CLOSE_ON_SERVER] = true;
           end_batch[grpc.opType.SEND_STATUS_FROM_SERVER] = {
-            metadata: {},
+            metadata: {metadata: {}},
             code: constants.status.OK,
             details: status_text
           };
diff --git a/packages/grpc-native-core/test/surface_test.js b/packages/grpc-native-core/test/surface_test.js
index bc745957..75183d5e 100644
--- a/packages/grpc-native-core/test/surface_test.js
+++ b/packages/grpc-native-core/test/surface_test.js
@@ -934,6 +934,19 @@ describe('Other conditions', function() {
     call.write({});
     call.end();
   });
+  it('client should drop a call if not connected with waitForReady off', function(done) {
+    /* We have to wait for the client to reach the first connection timeout
+     * and go to TRANSIENT_FAILURE to confirm that the waitForReady option
+     * makes it end the call instead of continuing to try. A DNS resolution
+     * failure makes that transition very fast. */
+    const disconnectedClient = new Client('nothing.invalid:50051', grpc.credentials.createInsecure());
+    const metadata = new grpc.Metadata({waitForReady: false});
+    disconnectedClient.unary({}, metadata, (error, value) =>{
+      assert(error);
+      assert.strictEqual(error.code, grpc.status.UNAVAILABLE);
+      done();
+    });
+  });
   describe('Server recieving bad input', function() {
     var misbehavingClient;
     var badArg = Buffer.from([0xFF]);