diff --git a/MANIFEST.in b/MANIFEST.in
new file mode 100644
index 0000000..ceeea23
--- /dev/null
+++ b/MANIFEST.in
@@ -0,0 +1 @@
+include VERSION
diff --git a/README.md b/README.md
index b2b8989..6cc333f 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@ response.id
 
 # you can optionally pass in a callback url that we'll POST to when the
 # batch is complete.
-response = client.batch(emails, callback_url='https://emailable.com/')
+response = client.batch(emails, {'callback_url': 'https://emailable.com/'})
 ```
 
 #### Get the status / results of a batch
diff --git a/VERSION b/VERSION
index 7ec1d6d..4a36342 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.1.0
+3.0.0
diff --git a/emailable/client.py b/emailable/client.py
index b8bf656..d73b79c 100644
--- a/emailable/client.py
+++ b/emailable/client.py
@@ -24,12 +24,11 @@ def verify(self, email, smtp=True, accept_all=False, timeout=None):
     url = self.base_url + 'verify'
     return self.__request('get', url, options)
 
-  def batch(self, emails, callback_url=None, simulate=None):
+  def batch(self, emails, params={}):
     options = {
       'params': {
-        'api_key': self.api_key,
-        'url': callback_url,
-        'simulate': simulate
+        **{'api_key': self.api_key},
+        **params
       },
       'json': {
         'emails': emails
diff --git a/tests/test_client.py b/tests/test_client.py
index 1b0e348..f0b1c3a 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -5,8 +5,7 @@
 class TestClient(TestCase):
   def setUp(self):
     self.client = emailable.Client('test_7aff7fc0142c65f86a00')
-    self.response = self.client.verify('johndoe+tag@emailable.com')
-    time.sleep(0.25)
+    time.sleep(0.5)
 
   def test_invalid_api_key(self):
     client = emailable.Client('test_7aff7fc0141c65f86a00')
@@ -25,7 +24,8 @@ def test_missing_api_key(self):
     )
 
   def test_verify_returns_response(self):
-    self.assertIsInstance(self.response, emailable.Response)
+    response = self.client.verify('johndoe+tag@emailable.com')
+    self.assertIsInstance(response, emailable.Response)
 
   def test_verification_role(self):
     response = self.client.verify('role@example.com')
@@ -36,26 +36,35 @@ def test_verification_deliverable(self):
     self.assertEqual(response.state, 'deliverable')
 
   def test_verification_tag(self):
-    self.assertEqual(self.response.tag, 'tag')
+    response = self.client.verify('johndoe+tag@emailable.com')
+    self.assertEqual(response.tag, 'tag')
 
   def test_verification_name_and_gender(self):
+    response = self.client.verify('johndoe+tag@emailable.com')
     # name and gender checks only get run for certain verification states
-    if self.response.state in ['deliverable', 'risky', 'unknown']:
-      self.assertEqual(self.response.first_name, 'John')
-      self.assertEqual(self.response.last_name, 'Doe')
-      self.assertEqual(self.response.full_name, 'John Doe')
-      self.assertEqual(self.response.gender, 'male')
+    if response.state in ['deliverable', 'risky', 'unknown']:
+      self.assertEqual(response.first_name, 'John')
+      self.assertEqual(response.last_name, 'Doe')
+      self.assertEqual(response.full_name, 'John Doe')
+      self.assertEqual(response.gender, 'male')
     else:
-      self.assertIsNone(self.response.first_name)
-      self.assertIsNone(self.response.last_name)
-      self.assertIsNone(self.response.full_name)
-      self.assertIsNone(self.response.gender)
+      self.assertIsNone(response.first_name)
+      self.assertIsNone(response.last_name)
+      self.assertIsNone(response.full_name)
+      self.assertIsNone(response.gender)
 
   def test_batch_creation(self):
     response = self.client.batch(
       ['evan@emailable.com', 'jarrett@emailable.com']
     )
     self.assertIsNotNone(response.id)
+  
+  def test_batch_creation_with_params(self):
+    with self.assertRaises(emailable.error.ClientError):
+      self.client.batch(
+        ['evan@emailable.com', 'jarrett@emailable.com'],
+        {'callback_url': 'test@example.org', 'simulate': 'generic_error'}
+      )
 
   def test_batch_status(self):
     response = self.client.batch(