diff --git a/solvebio/__init__.py b/solvebio/__init__.py
index 53732340..3f31722b 100644
--- a/solvebio/__init__.py
+++ b/solvebio/__init__.py
@@ -118,8 +118,7 @@ def emit(self, record):
 
 
 def login(**kwargs):
-    """
-    Sets up the auth credentials using the provided key/token,
+    """Sets up the auth credentials using the provided key/token,
     or checks the credentials file (if no token provided).
 
     Lookup order:
diff --git a/solvebio/errors.py b/solvebio/errors.py
index a1cc2318..ff6aac4d 100644
--- a/solvebio/errors.py
+++ b/solvebio/errors.py
@@ -46,15 +46,16 @@ def __init__(self, message=None, response=None):
             elif response.status_code == 404:
                 self.message = '404 Not Found ({})'.format(response.url)
 
-            # Handle other keys
-            for k, v in list(self.json_body.items()):
-                if k in ["non_field_errors", "detail"]:
-                    self.message += '\nError: '
-                else:
-                    self.message += '\nError (%s): ' % k
-
-                # can be a list, dict, string
-                self.message += str(v)
+            if self.json_body:
+                # Handle other keys
+                for k, v in list(self.json_body.items()):
+                    if k in ["non_field_errors", "detail"]:
+                        self.message += '\nError: '
+                    else:
+                        self.message += '\nError (%s): ' % k
+
+                    # can be a list, dict, string
+                    self.message += str(v)
 
     def __str__(self):
         return self.message
diff --git a/solvebio/resource/apiresource.py b/solvebio/resource/apiresource.py
index c84c13b8..b6fcfa3d 100644
--- a/solvebio/resource/apiresource.py
+++ b/solvebio/resource/apiresource.py
@@ -45,16 +45,10 @@ def class_name(cls):
                 'actions on its subclasses (e.g. Vault, Object, Dataset)')
         return str(quote_plus(cls.__name__))
 
-    @classmethod
-    def class_url(cls):
-        """Returns a versioned URI string for this class"""
-        base = 'v{0}'.format(getattr(cls, 'RESOURCE_VERSION', '1'))
-        return "/{0}/{1}".format(base, class_to_api_name(cls.class_name()))
-
     def instance_url(self):
         """Get instance URL by ID"""
         id_ = self.get(self.ID_ATTR)
-        base = self.class_url()
+        base = self.RESOURCE
 
         if id_:
             return '/'.join([base, six.text_type(id_)])
@@ -68,7 +62,7 @@ def instance_url(self):
 class ListObject(SolveObject):
 
     def all(self, **params):
-        """Lists all items in a class that you have access to"""
+        """Lists all resources that you have access to"""
         return self.request('get', self['url'], params=params)
 
     def create(self, **params):
@@ -142,18 +136,8 @@ def retrieve(cls, **kwargs):
         _client = kwargs.pop('client', None) or cls._client or client
         return super(SingletonAPIResource, cls).retrieve(None, client=_client)
 
-    @classmethod
-    def class_url(cls):
-        """
-        Returns a versioned URI string for this class,
-        and don't pluralize the class name.
-        """
-        base = 'v{0}'.format(getattr(cls, 'RESOURCE_VERSION', '1'))
-        return "/{0}/{1}".format(base, class_to_api_name(
-            cls.class_name(), pluralize=False))
-
     def instance_url(self):
-        return self.class_url()
+        return self.RESOURCE
 
 
 class CreateableAPIResource(APIResource):
@@ -161,8 +145,7 @@ class CreateableAPIResource(APIResource):
     @classmethod
     def create(cls, **params):
         _client = params.pop('client', None) or cls._client or client
-        url = cls.class_url()
-        response = _client.post(url, data=params)
+        response = _client.post(cls.RESOURCE, data=params)
         return convert_to_solve_object(response, client=_client)
 
 
@@ -241,8 +224,7 @@ class ListableAPIResource(APIResource):
     @classmethod
     def all(cls, **params):
         _client = params.pop('client', None) or cls._client or client
-        url = cls.class_url()
-        response = _client.get(url, params)
+        response = _client.get(cls.RESOURCE, params)
         results = convert_to_solve_object(response, client=_client)
 
         # If the object has LIST_FIELDS, setup tabulate
@@ -257,8 +239,7 @@ def all(cls, **params):
     @classmethod
     def _retrieve_helper(cls, model_name, field_name, error_value, **params):
         _client = params.pop('client', None) or cls._client or client
-        url = cls.class_url()
-        response = _client.get(url, params)
+        response = _client.get(cls.RESOURCE, params)
         results = convert_to_solve_object(response, client=_client)
         objects = results.data
         allow_multiple = params.pop('allow_multiple', None)
@@ -289,8 +270,7 @@ class SearchableAPIResource(APIResource):
     def search(cls, query='', **params):
         _client = params.pop('client', None) or cls._client or client
         params.update({'q': query})
-        url = cls.class_url()
-        response = _client.get(url, params)
+        response = _client.get(cls.RESOURCE, params)
         results = convert_to_solve_object(response, client=_client)
 
         # If the object has LIST_FIELDS, setup tabulate
@@ -306,8 +286,14 @@ def search(cls, query='', **params):
 class UpdateableAPIResource(APIResource):
 
     def save(self):
-        self.refresh_from(self.request('patch', self.instance_url(),
-                                       data=self.serialize(self)))
+        # If the class is "createable" and has no ID, try to create it
+        if self.get(self.ID_ATTR) is None and getattr(self, 'create'):
+            self.refresh_from(self.request('post', self.RESOURCE,
+                                           data=self.serialize(self)))
+        else:
+            self.refresh_from(self.request('patch', self.instance_url(),
+                                           data=self.serialize(self)))
+
         return self
 
     def serialize(self, obj):
diff --git a/solvebio/resource/application.py b/solvebio/resource/application.py
index e747316a..7d674dec 100644
--- a/solvebio/resource/application.py
+++ b/solvebio/resource/application.py
@@ -12,7 +12,7 @@ class Application(CreateableAPIResource,
                   SearchableAPIResource,
                   UpdateableAPIResource):
     ID_ATTR = 'client_id'
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/applications'
 
     LIST_FIELDS = (
         ('client_id', 'Client ID'),
diff --git a/solvebio/resource/beacon.py b/solvebio/resource/beacon.py
index 9d895e6d..2fb6aa85 100644
--- a/solvebio/resource/beacon.py
+++ b/solvebio/resource/beacon.py
@@ -12,7 +12,7 @@ class Beacon(CreateableAPIResource,
     Beacons provide entity-based search endpoints for datasets. Beacons
     must be created within Beacon Sets.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/beacons'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/beaconset.py b/solvebio/resource/beaconset.py
index f6ffba29..cbf2e29f 100644
--- a/solvebio/resource/beaconset.py
+++ b/solvebio/resource/beaconset.py
@@ -13,7 +13,7 @@ class BeaconSet(CreateableAPIResource,
     entity-based search endpoints for datasets. Beacon sets can be
     used to query a group of related datasets in a single API request.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/beacon_sets'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/dataset.py b/solvebio/resource/dataset.py
index 51998df3..c379c904 100644
--- a/solvebio/resource/dataset.py
+++ b/solvebio/resource/dataset.py
@@ -24,7 +24,7 @@ class Dataset(CreateableAPIResource,
     Datasets are access points to data. Dataset names are unique
     within a vault folder.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/datasets'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/datasetcommit.py b/solvebio/resource/datasetcommit.py
index 8d49d9a2..18d29f98 100644
--- a/solvebio/resource/datasetcommit.py
+++ b/solvebio/resource/datasetcommit.py
@@ -38,7 +38,7 @@ class DatasetCommit(CreateableAPIResource, ListableAPIResource,
     """
     DatasetCommits represent a change made to a Dataset.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/dataset_commits'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/datasetexport.py b/solvebio/resource/datasetexport.py
index fd20a166..9fd49519 100644
--- a/solvebio/resource/datasetexport.py
+++ b/solvebio/resource/datasetexport.py
@@ -17,7 +17,7 @@ class DatasetExport(CreateableAPIResource, ListableAPIResource,
     For interactive use, DatasetExport can be "followed" to watch
     the progression of the task.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/dataset_exports'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/datasetfield.py b/solvebio/resource/datasetfield.py
index 22ab7d58..21b62ad1 100644
--- a/solvebio/resource/datasetfield.py
+++ b/solvebio/resource/datasetfield.py
@@ -5,6 +5,8 @@
 from .apiresource import UpdateableAPIResource
 from .apiresource import DeletableAPIResource
 
+from ..annotate import Expression
+
 
 class DatasetField(CreateableAPIResource,
                    ListableAPIResource,
@@ -15,7 +17,7 @@ class DatasetField(CreateableAPIResource,
     which can be used as filters. Dataset field resources provide
     users with documentation about each field.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/dataset_fields'
 
     def facets(self, **params):
         response = self._client.get(self.facets_url, params)
@@ -23,3 +25,10 @@ def facets(self, **params):
 
     def help(self):
         return self.facets()
+
+    def evaluate(self):
+        if not self.get('expression'):
+            return None
+
+        return Expression(self['expression'], client=self._client).evaluate(
+            data_type=self.get('data_type', 'string'))
diff --git a/solvebio/resource/datasetimport.py b/solvebio/resource/datasetimport.py
index 8b1e4593..ed5a3e9b 100644
--- a/solvebio/resource/datasetimport.py
+++ b/solvebio/resource/datasetimport.py
@@ -20,7 +20,7 @@ class DatasetImport(CreateableAPIResource, ListableAPIResource,
     For interactive use, DatasetImport can be "followed" to watch
     the progression of an import job.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/dataset_imports'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/datasetmigration.py b/solvebio/resource/datasetmigration.py
index 43a26b68..2d5b4e08 100644
--- a/solvebio/resource/datasetmigration.py
+++ b/solvebio/resource/datasetmigration.py
@@ -17,7 +17,7 @@ class DatasetMigration(CreateableAPIResource, ListableAPIResource,
     For interactive use, DatasetMigration can be "followed" to watch
     the progression of the task.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/dataset_migrations'
 
     LIST_FIELDS = (
         ('id', 'ID'),
@@ -55,9 +55,8 @@ def follow(self, loop=True, sleep_seconds=Task.SLEEP_WAIT_DEFAULT):
                 processed_records = self.metadata\
                     .get('progress', {})\
                     .get('processed_records', 0)
-                print("Migration '{0}' is {1}: {2}/{3} records migrated"
+                print("Migration '{}' is running: {}/{} records migrated"
                       .format(self.id,
-                              self.status,
                               processed_records,
                               self.documents_count))
 
diff --git a/solvebio/resource/datasettemplate.py b/solvebio/resource/datasettemplate.py
index b5008162..9bcddcc3 100644
--- a/solvebio/resource/datasettemplate.py
+++ b/solvebio/resource/datasettemplate.py
@@ -3,6 +3,12 @@
 from .apiresource import UpdateableAPIResource
 from .apiresource import DeletableAPIResource
 
+from . import DatasetField
+
+import re
+import inspect
+from itertools import dropwhile
+
 
 class DatasetTemplate(CreateableAPIResource, ListableAPIResource,
                       UpdateableAPIResource, DeletableAPIResource):
@@ -10,7 +16,7 @@ class DatasetTemplate(CreateableAPIResource, ListableAPIResource,
     DatasetTemplates contain the schema of a Dataset, including some
     properties and all the fields.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/dataset_templates'
 
     LIST_FIELDS = (
         ('id', 'ID'),
@@ -18,6 +24,36 @@ class DatasetTemplate(CreateableAPIResource, ListableAPIResource,
         ('description', 'Description'),
     )
 
+    def __init__(self, *args, **kwargs):
+        super(DatasetTemplate, self).__init__(*args, **kwargs)
+        self.fields = self.__init_fields(**kwargs)
+
+    @classmethod
+    def __init_fields(cls, *args, **kwargs):
+        fields = kwargs.get("fields") or []
+        for attr in dir(cls):
+            if attr.startswith("__"):
+                continue
+
+            func = getattr(cls, attr, None)
+            if getattr(func, "field", None):
+                fields.append(func.field)
+
+        return fields
+
+    @classmethod
+    def create(cls, **params):
+        params["fields"] = cls.__init_fields(**params)
+        return super(DatasetTemplate, cls).create(**params)
+
+    @classmethod
+    def get_or_create_by_name(cls, name, **params):
+        objects = cls.all(name=name, **params).solve_objects()
+        if objects:
+            return objects[0]
+
+        return cls.create(name=name, **params)
+
     @property
     def import_params(self):
         """
@@ -31,3 +67,36 @@ def import_params(self):
             'annotator_params': self.annotator_params,
             'validation_params': self.validation_params
         }
+
+    @staticmethod
+    def field(*args, **kwargs):
+        def get_function_body(func):
+            source_lines = inspect.getsourcelines(func)[0]
+            source_lines = dropwhile(lambda x: x.startswith('@'), source_lines)
+            source = ''.join(source_lines)
+            # Remove comments
+            source = re.sub(r'(?m)^ *#.*\n?', '', source)
+            pattern = re.compile(
+                r'(async\s+)?def\s+\w+\s*\(.*?\)\s*:\s*(.*)',
+                flags=re.S)
+            lines = pattern.search(source).group(2).splitlines()
+            if len(lines) == 1:
+                body = lines[0]
+            else:
+                # Dedent the code
+                indentation = len(lines[1]) - len(lines[1].lstrip())
+                body = '\n'.join(
+                    [lines[0]] +
+                    [line[indentation:] for line in lines[1:]]
+                )
+
+            # Remove any return statement
+            return body.replace('return ', '')
+
+        def decorator(f):
+            kwargs['name'] = f.__name__
+            kwargs['expression'] = get_function_body(f)
+            f.field = DatasetField(*args, **kwargs)
+            return f
+
+        return decorator
diff --git a/solvebio/resource/group.py b/solvebio/resource/group.py
index 6c065a58..45ef9b80 100644
--- a/solvebio/resource/group.py
+++ b/solvebio/resource/group.py
@@ -10,7 +10,7 @@ class Group(CreateableAPIResource, ListableAPIResource,
     """
     A Group represents a group of users with shared permissions for a vault.
     """
-    RESOURCE_VERSION = 1
+    RESOURCE = '/v1/groups'
 
     LIST_FIELDS = (
         ('id', 'ID'),
@@ -47,7 +47,7 @@ def vaults(self, **params):
     def datasets(self, **params):
         from . import Object
         vaults = self._get_vaults(**params)
-        objects_url = Object.class_url() + '?object_type=dataset&' + \
+        objects_url = Object.RESOURCE + '?object_type=dataset&' + \
             '&'.join(['vault_id={0}'.format(v.id) for v in vaults])
         response = self._client.get(objects_url, params)
         datasets = convert_to_solve_object(response, client=self._client)
diff --git a/solvebio/resource/object.py b/solvebio/resource/object.py
index c4a21691..5fc8c099 100644
--- a/solvebio/resource/object.py
+++ b/solvebio/resource/object.py
@@ -35,7 +35,7 @@ class Object(CreateableAPIResource,
     An object is a resource in a Vault.  It has three possible types,
     though more may be added later: folder, file, and SolveBio Dataset.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/objects'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/object_copy_task.py b/solvebio/resource/object_copy_task.py
index e49b9725..8b19ad56 100644
--- a/solvebio/resource/object_copy_task.py
+++ b/solvebio/resource/object_copy_task.py
@@ -9,7 +9,7 @@
 class ObjectCopyTask(CreateableAPIResource,
                      ListableAPIResource,
                      UpdateableAPIResource):
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/object_copy_tasks'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/savedquery.py b/solvebio/resource/savedquery.py
index 49c1e728..ce84fd15 100644
--- a/solvebio/resource/savedquery.py
+++ b/solvebio/resource/savedquery.py
@@ -14,7 +14,7 @@ class SavedQuery(CreateableAPIResource, ListableAPIResource,
     with ease. A dataset is said to be compatible with a saved query
     if it contains all the fields found in said saved query.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/saved_queries'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/solveobject.py b/solvebio/resource/solveobject.py
index ac82ebe5..00560abf 100644
--- a/solvebio/resource/solveobject.py
+++ b/solvebio/resource/solveobject.py
@@ -30,6 +30,7 @@ def convert_to_solve_object(resp, **kwargs):
 class SolveObject(dict):
     """Base class for all SolveBio API resource objects"""
     ID_ATTR = 'id'
+    RESOURCE = None
 
     # Allows pre-setting a SolveClient
     _client = None
@@ -45,6 +46,9 @@ def __init__(self, id=None, **params):
         if id:
             self[self.ID_ATTR] = id
 
+        for k, v in list(params.items()):
+            self[k] = v
+
     def __setattr__(self, k, v):
         if k[0] == '_' or k in self.__dict__:
             return super(SolveObject, self).__setattr__(k, v)
diff --git a/solvebio/resource/task.py b/solvebio/resource/task.py
index 607c6d4d..aa1eb254 100644
--- a/solvebio/resource/task.py
+++ b/solvebio/resource/task.py
@@ -7,7 +7,7 @@ class Task(ListableAPIResource, UpdateableAPIResource):
     """
     Tasks are operations on datasets or vaults.
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/tasks'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/user.py b/solvebio/resource/user.py
index 84a734e3..d831dcc5 100644
--- a/solvebio/resource/user.py
+++ b/solvebio/resource/user.py
@@ -3,4 +3,4 @@
 
 
 class User(SingletonAPIResource):
-    pass
+    RESOURCE = '/v1/user'
diff --git a/solvebio/resource/vault.py b/solvebio/resource/vault.py
index a834efb2..b4f608b9 100644
--- a/solvebio/resource/vault.py
+++ b/solvebio/resource/vault.py
@@ -23,7 +23,7 @@ class Vault(CreateableAPIResource,
     Typically, vaults contain a series of datasets that are compatible with
     each other (i.e. they come from the same data source or project).
     """
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/vaults'
 
     LIST_FIELDS = (
         ('id', 'ID'),
diff --git a/solvebio/resource/vault_sync_task.py b/solvebio/resource/vault_sync_task.py
index 8dff79cd..38325ef9 100644
--- a/solvebio/resource/vault_sync_task.py
+++ b/solvebio/resource/vault_sync_task.py
@@ -9,7 +9,7 @@
 class VaultSyncTask(CreateableAPIResource,
                     ListableAPIResource,
                     UpdateableAPIResource):
-    RESOURCE_VERSION = 2
+    RESOURCE = '/v2/vault_sync_tasks'
 
     LIST_FIELDS = (
         ('id', 'ID'),