diff --git a/mopidy/exceptions.py b/mopidy/exceptions.py
index 32a2bd9a..d02a288a 100644
--- a/mopidy/exceptions.py
+++ b/mopidy/exceptions.py
@@ -46,3 +46,7 @@ class ScannerError(MopidyException):
 
 class AudioException(MopidyException):
     pass
+
+
+class ValidationError(ValueError):
+    pass
diff --git a/mopidy/utils/validation.py b/mopidy/utils/validation.py
new file mode 100644
index 00000000..a0306564
--- /dev/null
+++ b/mopidy/utils/validation.py
@@ -0,0 +1,102 @@
+from __future__ import absolute_import, unicode_literals
+
+import collections
+import urlparse
+
+from mopidy import compat, exceptions
+
+PLAYBACK_STATES = {'paused', 'stopped', 'playing'}
+
+QUERY_FIELDS = {
+    'uri', 'track_name', 'album', 'artist', 'albumartist', 'composer',
+    'performer', 'track_no', 'genre', 'date', 'comment', 'any', 'tlid', 'name'}
+
+DISTINCT_FIELDS = {
+    'artist', 'albumartist', 'album', 'composer', 'performer', 'date', 'genre'}
+
+
+# TODO: _check_iterable(check, msg, **kwargs) + [check(a) for a in arg]?
+def _check_iterable(arg, msg, **kwargs):
+    """Ensure we have an iterable which is not a string."""
+    if isinstance(arg, compat.string_types):
+        raise exceptions.ValidationError(msg.format(arg=arg, **kwargs))
+    elif not isinstance(arg, collections.Iterable):
+        raise exceptions.ValidationError(msg.format(arg=arg, **kwargs))
+
+
+def check_choice(arg, choices, msg='Expected one of {choices}, not {arg!r}'):
+    if arg not in choices:
+        raise exceptions.ValidationError(msg.format(
+            arg=arg, choices=tuple(choices)))
+
+
+def check_boolean(arg, msg='Expected a boolean, not {arg!r}'):
+    check_instance(arg, bool, msg=msg)
+
+
+def check_instance(arg, cls, msg='Expected a {name} instance, not {arg!r}'):
+    if not isinstance(arg, cls):
+        raise exceptions.ValidationError(
+            msg.format(arg=arg, name=cls.__name__))
+
+
+def check_instances(arg, cls, msg='Expected a list of {name}, not {arg!r}'):
+    _check_iterable(arg, msg, name=cls.__name__)
+    if not all(isinstance(instance, cls) for instance in arg):
+        raise exceptions.ValidationError(
+            msg.format(arg=arg, name=cls.__name__))
+
+
+def check_integer(arg, min=None, max=None):
+    if not isinstance(arg, (int, long)):
+        raise exceptions.ValidationError('Expected an integer, not %r' % arg)
+    elif min is not None and arg < min:
+        raise exceptions.ValidationError(
+            'Expected number larger or equal to %d, not %r' % (min, arg))
+    elif max is not None and arg > max:
+        raise exceptions.ValidationError(
+            'Expected number smaller or equal to %d, not %r' % (max, arg))
+
+
+def check_query(arg, list_values=True):
+    # TODO: normalize name  -> track_name
+    # TODO: normalize value -> [value]
+    # TODO: normalize blank -> [] or just remove field?
+    # TODO: normalize int -> str or remove int support?
+    # TODO: remove list_values?
+    # TODO: don't allow for instance tlid field in all queries?
+
+    if not isinstance(arg, collections.Mapping):
+        raise exceptions.ValidationError(
+            'Expected a query dictionary, not {arg!r}'.format(arg=arg))
+
+    for key, value in arg.items():
+        check_choice(key, QUERY_FIELDS, msg='Expected query field to be one '
+                     'of {choices}, not {arg!r}')
+        if list_values:
+            msg = 'Expected "{key}" values to be list of strings, not {arg!r}'
+            _check_iterable(value, msg, key=key)
+            [_check_query_value(key, v, msg) for v in value]
+        else:
+            _check_query_value(key, value, 'Expected "{key}" value to be a '
+                               'string, not {arg!r}')
+
+
+def _check_query_value(key, arg, msg):
+    if isinstance(arg, compat.string_types):
+        if not arg.strip():
+            raise exceptions.ValidationError(msg.format(arg=arg, key=key))
+    elif not isinstance(arg, (int, long)):
+        raise exceptions.ValidationError(msg.format(arg=arg, key=key))
+
+
+def check_uri(arg, msg='Expected a valid URI, not {arg!r}'):
+    if not isinstance(arg, compat.string_types):
+        raise exceptions.ValidationError(msg.format(arg=arg))
+    elif urlparse.urlparse(arg).scheme == '':
+        raise exceptions.ValidationError(msg.format(arg=arg))
+
+
+def check_uris(arg, msg='Expected a list of URIs, not {arg!r}'):
+    _check_iterable(arg, msg)
+    [check_uri(a, msg) for a in arg]
diff --git a/tests/utils/test_validation.py b/tests/utils/test_validation.py
new file mode 100644
index 00000000..d55a918e
--- /dev/null
+++ b/tests/utils/test_validation.py
@@ -0,0 +1,163 @@
+from __future__ import absolute_import, unicode_literals
+
+from pytest import raises
+
+from mopidy import compat, exceptions
+from mopidy.utils import validation
+
+
+def test_check_boolean_with_valid_values():
+    for value in (True, False):
+        validation.check_boolean(value)
+
+
+def test_check_boolean_with_truthy_values():
+    for value in 1, 0, None, '', list(), tuple():
+        with raises(exceptions.ValidationError):
+            validation.check_boolean(value)
+
+
+def test_check_boolean_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_boolean(1234)
+    assert 'Expected a boolean, not 1234' == str(excinfo.value)
+
+
+def test_check_choice_with_valid_values():
+    for value, choices in (2, (1, 2, 3)), ('abc', ('abc', 'def')):
+        validation.check_choice(value, choices)
+
+
+def test_check_choice_with_invalid_values():
+    for value, choices in (5, (1, 2, 3)), ('xyz', ('abc', 'def')):
+        with raises(exceptions.ValidationError):
+            validation.check_choice(value, choices)
+
+
+def test_check_choice_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_choice(5, (1, 2, 3))
+    assert 'Expected one of (1, 2, 3), not 5' == str(excinfo.value)
+
+
+def test_check_instance_with_valid_choices():
+    for value, cls in ((True, bool), ('a', compat.text_type), (123, int)):
+        validation.check_instance(value, cls)
+
+
+def test_check_instance_with_invalid_values():
+    for value, cls in (1, str), ('abc', int):
+        with raises(exceptions.ValidationError):
+            validation.check_instance(value, cls)
+
+
+def test_check_instance_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_instance(1, dict)
+    assert 'Expected a dict instance, not 1' == str(excinfo.value)
+
+
+def test_check_instances_with_valid_values():
+    validation.check_instances([], int)
+    validation.check_instances([1, 2], int)
+    validation.check_instances((1, 2), int)
+
+
+def test_check_instances_with_invalid_values():
+    with raises(exceptions.ValidationError):
+        validation.check_instances('abc', compat.string_types)
+    with raises(exceptions.ValidationError):
+        validation.check_instances(['abc', 123], compat.string_types)
+    with raises(exceptions.ValidationError):
+        validation.check_instances(None, compat.string_types)
+    with raises(exceptions.ValidationError):
+        validation.check_instances([None], compat.string_types)
+
+
+def test_check_instances_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_instances([1], compat.string_types)
+    assert 'Expected a list of basestring, not [1]' == str(excinfo.value)
+
+
+def test_check_query_valid_values():
+    for value in {}, {'any': []}, {'any': ['abc']}:
+        validation.check_query(value)
+
+
+def test_check_query_random_iterables():
+    for value in None, tuple(), list(), 'abc':
+        with raises(exceptions.ValidationError):
+            validation.check_query(value)
+
+
+def test_check_mapping_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_query([])
+    assert 'Expected a query dictionary, not []' == str(excinfo.value)
+
+
+def test_check_query_invalid_fields():
+    for value in 'wrong', 'bar', 'foo':
+        with raises(exceptions.ValidationError):
+            validation.check_query({value: []})
+
+
+def test_check_field_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_query({'wrong': ['abc']})
+    assert 'Expected query field to be one of ' in str(excinfo.value)
+
+
+def test_check_query_invalid_values():
+    for value in '', None, 'foo', 123, [''], [None]:
+        with raises(exceptions.ValidationError):
+            validation.check_query({'any': value})
+
+
+def test_check_values_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_query({'any': 'abc'})
+    assert 'Expected "any" values to be list of strings' in str(excinfo.value)
+
+
+def test_check_uri_with_valid_values():
+    for value in 'foobar:', 'http://example.com', 'git+http://example.com':
+        validation.check_uri(value)
+
+
+def test_check_uri_with_invalid_values():
+    # Note that tuple catches a potential bug with using "'foo' % arg" for
+    # formatting.
+    for value in ('foobar', 'htt p://example.com', None, 1234, tuple()):
+        with raises(exceptions.ValidationError):
+            validation.check_uri(value)
+
+
+def test_check_uri_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_uri('testing')
+    assert "Expected a valid URI, not u'testing'" == str(excinfo.value)
+
+
+def test_check_uris_with_valid_values():
+    validation.check_uris([])
+    validation.check_uris(['foobar:'])
+    validation.check_uris(('foobar:',))
+
+
+def test_check_uris_with_invalid_values():
+    with raises(exceptions.ValidationError):
+        validation.check_uris('foobar:')
+    with raises(exceptions.ValidationError):
+        validation.check_uris(None)
+    with raises(exceptions.ValidationError):
+        validation.check_uris([None])
+    with raises(exceptions.ValidationError):
+        validation.check_uris(['foobar:', 'foobar'])
+
+
+def test_check_uris_error_message():
+    with raises(exceptions.ValidationError) as excinfo:
+        validation.check_uris('testing')
+    assert "Expected a list of URIs, not u'testing'" == str(excinfo.value)