diff --git a/planet/cli/cli.py b/planet/cli/cli.py
index 41cf057..d75eb33 100644
--- a/planet/cli/cli.py
+++ b/planet/cli/cli.py
@@ -27,20 +27,17 @@ LOGGER = logging.getLogger(__name__)
 
 @click.group()
 @click.pass_context
-@click.option('--verbosity',
-              default="warning",
-              help=("Optional: set verbosity level to warning, info, or debug.\
-                  Defaults to warning."))
 @click.option('--quiet',
               is_flag=True,
               default=False,
               help='Disable ANSI control output.')
 @click.version_option(version=planet.__version__)
+@click.option('--verbosity',
+              default="warning",
+              help=("Optional: set verbosity level to warning, info, or debug.\
+                  Defaults to warning."))
 def main(ctx, verbosity, quiet):
-    """Planet API Client
-    Parameters:
-        ctx -- context object
-        verbosity -- user input for verbosity."""
+    """Planet SDK for Python CLI"""
     _configure_logging(verbosity)
 
     # ensure that ctx.obj exists and is a dict (in case `cli()` is called
diff --git a/planet/cli/data.py b/planet/cli/data.py
index 5f13850..1abdcde 100644
--- a/planet/cli/data.py
+++ b/planet/cli/data.py
@@ -19,6 +19,7 @@ import click
 
 from planet import data_filter, DataClient
 from planet.clients.data import SEARCH_SORT, SEARCH_SORT_DEFAULT, STATS_INTERVAL
+from planet.specs import get_item_types
 
 from . import types
 from .cmds import coro, translate_exceptions
@@ -26,6 +27,9 @@ from .io import echo_json
 from .options import limit, pretty
 from .session import CliSession
 
+ALL_ITEM_TYPES = get_item_types()
+valid_item_string = "Valid entries for ITEM_TYPES: " + "|".join(ALL_ITEM_TYPES)
+
 
 @asynccontextmanager
 async def data_client(ctx):
@@ -43,7 +47,7 @@ async def data_client(ctx):
               default=None,
               help='Assign custom base Orders API URL.')
 def data(ctx, base_url):
-    '''Commands for interacting with the Orders API'''
+    '''Commands for interacting with the Data API'''
     ctx.obj['AUTH'] = None
     ctx.obj['BASE_URL'] = base_url
 
@@ -58,6 +62,17 @@ def assets_to_filter(ctx, param, assets: List[str]) -> Optional[dict]:
     return data_filter.asset_filter(assets) if assets else None
 
 
+def check_item_types(ctx, param, item_types) -> Optional[List[dict]]:
+    # Set difference between given item types and all item types
+    set_diff = set([item.lower() for item in item_types]) - set(
+        [a.lower() for a in ALL_ITEM_TYPES])
+    if set_diff:
+        raise click.BadParameter(
+            f'{item_types} should be one of {ALL_ITEM_TYPES}')
+    else:
+        return item_types
+
+
 def date_range_to_filter(ctx, param, values) -> Optional[List[dict]]:
 
     def _func(obj):
@@ -226,11 +241,13 @@ def filter(ctx,
         echo_json(filt, pretty)
 
 
-@data.command()
+@data.command(epilog=valid_item_string)
 @click.pass_context
 @translate_exceptions
 @coro
-@click.argument("item_types", type=types.CommaSeparatedString())
+@click.argument("item_types",
+                type=types.CommaSeparatedString(),
+                callback=check_item_types)
 @click.argument("filter", type=types.JSON(), default="-", required=False)
 @limit
 @click.option('--name', type=str, help='Name of the saved search.')
@@ -264,12 +281,14 @@ async def search(ctx, item_types, filter, limit, name, sort, pretty):
             echo_json(item, pretty)
 
 
-@data.command()
+@data.command(epilog=valid_item_string)
 @click.pass_context
 @translate_exceptions
 @coro
 @click.argument('name')
-@click.argument("item_types", type=types.CommaSeparatedString())
+@click.argument("item_types",
+                type=types.CommaSeparatedString(),
+                callback=check_item_types)
 @click.argument("filter", type=types.JSON(), default="-", required=False)
 @click.option('--daily-email',
               is_flag=True,
@@ -296,11 +315,13 @@ async def search_create(ctx, name, item_types, filter, daily_email, pretty):
         echo_json(items, pretty)
 
 
-@data.command()
+@data.command(epilog=valid_item_string)
 @click.pass_context
 @translate_exceptions
 @coro
-@click.argument("item_types", type=types.CommaSeparatedString())
+@click.argument("item_types",
+                type=types.CommaSeparatedString(),
+                callback=check_item_types)
 @click.argument('interval', type=click.Choice(STATS_INTERVAL))
 @click.argument("filter", type=types.JSON(), default="-", required=False)
 async def stats(ctx, item_types, interval, filter):
diff --git a/planet/cli/subscriptions.py b/planet/cli/subscriptions.py
index 3f465a0..95b7f9e 100644
--- a/planet/cli/subscriptions.py
+++ b/planet/cli/subscriptions.py
@@ -13,6 +13,7 @@ from planet.clients.subscriptions import SubscriptionsClient
 @click.group()
 @click.pass_context
 def subscriptions(ctx):
+    '''Commands for interacting with the Subscriptions API'''
     # None means that order of precedence is 1) environment variable,
     # 2) secret file.
     ctx.obj['AUTH'] = None
diff --git a/planet/specs.py b/planet/specs.py
index f3971ab..0f8c155 100644
--- a/planet/specs.py
+++ b/planet/specs.py
@@ -93,10 +93,10 @@ def get_match(test_entry, spec_entries):
     is hard to remember but must be exact otherwise the API throws an
     exception.'''
     try:
-        match = next(t for t in spec_entries
-                     if t.lower() == test_entry.lower())
+        match = next(e for e in spec_entries
+                     if e.lower() == test_entry.lower())
     except (StopIteration):
-        raise NoMatchException
+        raise NoMatchException('{test_entry} should be one of {spec_entries}')
 
     return match
 
@@ -107,10 +107,19 @@ def get_product_bundles():
     return spec['bundles'].keys()
 
 
-def get_item_types(product_bundle):
-    '''Get item types supported by Orders API for the given product bundle.'''
+def get_item_types(product_bundle=None):
+    '''If given product bundle, get specific item types supported by Orders
+    API. Otherwise, get all item types supported by Orders API.'''
     spec = _get_product_bundle_spec()
-    return spec['bundles'][product_bundle]['assets'].keys()
+    if product_bundle:
+        item_types = spec['bundles'][product_bundle]['assets'].keys()
+    else:
+        product_bundle = get_product_bundles()
+        all_item_types = []
+        for bundle in product_bundle:
+            all_item_types += [*spec['bundles'][bundle]['assets'].keys()]
+        item_types = set(all_item_types)
+    return item_types
 
 
 def _get_product_bundle_spec():

diff --git a/tests/integration/test_data_cli.py b/tests/integration/test_data_cli.py
index 60a1a64..f146cf0 100644
--- a/tests/integration/test_data_cli.py
+++ b/tests/integration/test_data_cli.py
@@ -23,6 +23,7 @@ from click.testing import CliRunner
 import pytest
 
 from planet.cli import cli
+from planet.specs import get_item_types
 
 LOGGER = logging.getLogger(__name__)
 
@@ -55,6 +56,23 @@ def test_data_command_registered(invoke):
     # Add other sub-commands here.
 
 
+def test_data_search_command_registered(invoke):
+    """planet-data search command prints help and usage message."""
+    runner = CliRunner()
+    result = invoke(["search", "--help"], runner=runner)
+    all_item_types = [a for a in get_item_types()]
+    assert result.exit_code == 0
+    assert "Usage" in result.output
+    assert "limit" in result.output
+    assert "name" in result.output
+    assert "sort" in result.output
+    assert "pretty" in result.output
+    assert "help" in result.output
+    for a in all_item_types:
+        assert a in result.output.replace('\n', '').replace(' ', '')
+    # Add other sub-commands here.
+
+
 PERMISSION_FILTER = {"type": "PermissionFilter", "config": ["assets:download"]}
 STD_QUALITY_FILTER = {
     "type": "StringInFilter",
@@ -358,8 +376,8 @@ def test_data_filter_update(invoke, assert_and_filters_equal, default_filters):
 @respx.mock
 @pytest.mark.asyncio
 @pytest.mark.parametrize("filter", ['{1:1}', '{"foo"}'])
-@pytest.mark.parametrize(
-    "item_types", ['PSScene', 'SkySatScene', ('PSScene', 'SkySatScene')])
+@pytest.mark.parametrize("item_types",
+                         ['PSScene', 'SkySatScene', 'PSScene, SkySatScene'])
 def test_data_search_cmd_filter_invalid_json(invoke, item_types, filter):
     """Test for planet data search_quick. Test with multiple item_types.
     Test should fail as filter does not contain valid JSON."""
@@ -375,8 +393,8 @@ def test_data_search_cmd_filter_invalid_json(invoke, item_types, filter):
 
 
 @respx.mock
-@pytest.mark.parametrize(
-    "item_types", ['PSScene', 'SkySatScene', ('PSScene', 'SkySatScene')])
+@pytest.mark.parametrize("item_types",
+                         ['PSScene', 'SkySatScene', 'PSScene, SkySatScene'])
 def test_data_search_cmd_filter_success(invoke, item_types):
     """Test for planet data search_quick. Test with multiple item_types.
     Test should succeed as filter contains valid JSON."""
@@ -495,8 +513,8 @@ def test_data_search_cmd_limit(invoke,
 @respx.mock
 @pytest.mark.asyncio
 @pytest.mark.parametrize("filter", ['{1:1}', '{"foo"}'])
-@pytest.mark.parametrize(
-    "item_types", ['PSScene', 'SkySatScene', ('PSScene', 'SkySatScene')])
+@pytest.mark.parametrize("item_types",
+                         ['PSScene', 'SkySatScene', 'PSScene, SkySatScene'])
 def test_data_search_create_filter_invalid_json(invoke, item_types, filter):
     """Test for planet data search_create. Test with multiple item_types.
     Test should fail as filter does not contain valid JSON."""
@@ -514,8 +532,8 @@ def test_data_search_create_filter_invalid_json(invoke, item_types, filter):
 
 
 @respx.mock
-@pytest.mark.parametrize(
-    "item_types", ['PSScene', 'SkySatScene', ('PSScene', 'SkySatScene')])
+@pytest.mark.parametrize("item_types",
+                         ['PSScene', 'SkySatScene', 'PSScene, SkySatScene'])
 def test_data_search_create_filter_success(invoke, item_types):
     """Test for planet data search_create. Test with multiple item_types.
     Test should succeed as filter contains valid JSON."""
@@ -601,8 +619,8 @@ def test_data_stats_invalid_filter(invoke, filter):
 
 
 @respx.mock
-@pytest.mark.parametrize(
-    "item_types", ['PSScene', 'SkySatScene', ('PSScene', 'SkySatScene')])
+@pytest.mark.parametrize("item_types",
+                         ['PSScene', 'SkySatScene', 'PSScene, SkySatScene'])
 @pytest.mark.parametrize("interval, exit_code", [(None, 1), ('hou', 2),
                                                  ('hour', 0)])
 def test_data_stats_invalid_interval(invoke, item_types, interval, exit_code):
@@ -630,8 +648,8 @@ def test_data_stats_invalid_interval(invoke, item_types, interval, exit_code):
 
 
 @respx.mock
-@pytest.mark.parametrize(
-    "item_types", ['PSScene', 'SkySatScene', ('PSScene', 'SkySatScene')])
+@pytest.mark.parametrize("item_types",
+                         ['PSScene', 'SkySatScene', 'PSScene, SkySatScene'])
 @pytest.mark.parametrize("interval", ['hour', 'day', 'week', 'month', 'year'])
 def test_data_stats_success(invoke, item_types, interval):
     """Test for planet data stats. Test with multiple item_types.
diff --git a/tests/unit/test_data_item_type.py b/tests/unit/test_data_item_type.py
new file mode 100644
index 0000000..41d7b78
--- /dev/null
+++ b/tests/unit/test_data_item_type.py
@@ -0,0 +1,55 @@
+# Copyright 2022 Planet Labs PBC.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import logging
+import pytest
+import click
+from planet.cli.data import check_item_types
+
+LOGGER = logging.getLogger(__name__)
+
+
+class MockContext:
+
+    def __init__(self):
+        self.obj = {}
+
+
+@pytest.mark.parametrize("item_types",
+                         [
+                             'PSScene3Band',
+                             'MOD09GQ',
+                             'MYD09GA',
+                             'REOrthoTile',
+                             'SkySatCollect',
+                             'SkySatScene',
+                             'MYD09GQ',
+                             'Landsat8L1G',
+                             'Sentinel2L1C',
+                             'MOD09GA',
+                             'Sentinel1',
+                             'PSScene',
+                             'PSOrthoTile',
+                             'PSScene4Band',
+                             'REScene'
+                         ])
+def test_item_type_success(item_types):
+    ctx = MockContext()
+    result = check_item_types(ctx, 'item_types', [item_types])
+    assert result == [item_types]
+
+
+def test_item_type_fail():
+    ctx = MockContext()
+    with pytest.raises(click.BadParameter):
+        check_item_types(ctx, 'item_type', "bad_item_type")
diff --git a/tests/unit/test_specs.py b/tests/unit/test_specs.py
index 6f721e9..21b4e57 100644
--- a/tests/unit/test_specs.py
+++ b/tests/unit/test_specs.py
@@ -23,6 +23,23 @@ LOGGER = logging.getLogger(__name__)
 TEST_PRODUCT_BUNDLE = 'visual'
 # must be a valid item type for TEST_PRODUCT_BUNDLE
 TEST_ITEM_TYPE = 'PSScene'
+ALL_ITEM_TYPES = [
+    'PSOrthoTile',
+    'Sentinel1',
+    'REOrthoTile',
+    'PSScene',
+    'PSScene4Band',
+    'Landsat8L1G',
+    'PSScene3Band',
+    'REScene',
+    'MOD09GA',
+    'MYD09GA',
+    'MOD09GQ',
+    'SkySatCollect',
+    'Sentinel2L1C',
+    'MYD09GQ',
+    'SkySatScene'
+]
 
 
 def test_get_type_match():
@@ -90,6 +107,12 @@ def test_get_product_bundles():
     assert TEST_PRODUCT_BUNDLE in bundles
 
 
-def test_get_item_types():
-    item_types = specs.get_item_types(TEST_PRODUCT_BUNDLE)
+def test_get_item_types_with_bundle():
+    item_types = specs.get_item_types(product_bundle=TEST_PRODUCT_BUNDLE)
     assert TEST_ITEM_TYPE in item_types
+
+
+def test_get_item_types_without_bundle():
+    item_types = specs.get_item_types()
+    for item in item_types:
+        assert item in ALL_ITEM_TYPES

Improve default CLI help
The message that pops up when you first try `planet` can use a few improvements:

```
planet --help
Usage: planet [OPTIONS] COMMAND [ARGS]...

  Planet API Client Parameters:     ctx -- context object     verbosity --
  user input for verbosity.

Options:
  --verbosity TEXT  Optional: set verbosity level to warning, info, or debug.
                    Defaults to warning.
  --quiet           Disable ANSI control output.
  --version         Show the version and exit.
  --help            Show this message and exit.

Commands:
  auth           Commands for working with Planet authentication
  collect        Collect a sequence of JSON descriptions into a single...
  data           Commands for interacting with the Orders API
  orders         Commands for interacting with the Orders API
  subscriptions
```

- [x] The third line is a bit strange, seems like it's about the API? `Planet API Client Parameters:     ctx -- context object     verbosity --
  user input for verbosity.` I'd say remove, unless there's something it's getting at I don't know?
    - [x] maybe put verbosity last in the 'options', as that seems the least likely to be used.
- [x] `data` says 'commands for interacting with the Orders API. Should be Data API.
- [x] subscriptions has no description.
tests/integration/test_data_cli.py::test_data_command_registered tests/integration/test_data_cli.py::test_data_search_command_registered tests/integration/test_data_cli.py::test_data_filter_defaults[None-None-None-None] tests/integration/test_data_cli.py::test_data_filter_defaults[None-None---permission=False-p_remove1] tests/integration/test_data_cli.py::test_data_filter_defaults[--std-quality=False-s_remove1-None-None] tests/integration/test_data_cli.py::test_data_filter_defaults[--std-quality=False-s_remove1---permission=False-p_remove1] tests/integration/test_data_cli.py::test_data_filter_asset[ortho_analytic_8b_sr-expected0] tests/integration/test_data_cli.py::test_data_filter_asset[ortho_analytic_8b_sr,ortho_analytic_4b_sr-expected1] tests/integration/test_data_cli.py::test_data_filter_asset[ortho_analytic_8b_sr tests/integration/test_data_cli.py::test_data_filter_date_range_success tests/integration/test_data_cli.py::test_data_filter_date_range_invalid tests/integration/test_data_cli.py::test_data_filter_geom[geom_geojson] tests/integration/test_data_cli.py::test_data_filter_geom[feature_geojson] tests/integration/test_data_cli.py::test_data_filter_geom[featurecollection_geojson] tests/integration/test_data_cli.py::test_data_filter_number_in_success tests/integration/test_data_cli.py::test_data_filter_number_in_badparam tests/integration/test_data_cli.py::test_data_filter_range tests/integration/test_data_cli.py::test_data_filter_string_in tests/integration/test_data_cli.py::test_data_filter_update tests/integration/test_data_cli.py::test_data_search_cmd_filter_invalid_json[PSScene-{1:1}] tests/integration/test_data_cli.py::test_data_search_cmd_filter_invalid_json[PSScene-{"foo"}] tests/integration/test_data_cli.py::test_data_search_cmd_filter_invalid_json[SkySatScene-{1:1}] tests/integration/test_data_cli.py::test_data_search_cmd_filter_invalid_json[SkySatScene-{"foo"}] tests/integration/test_data_cli.py::test_data_search_cmd_filter_invalid_json[PSScene, tests/integration/test_data_cli.py::test_data_search_cmd_filter_success[PSScene] tests/integration/test_data_cli.py::test_data_search_cmd_filter_success[SkySatScene] tests/integration/test_data_cli.py::test_data_search_cmd_filter_success[PSScene, tests/integration/test_data_cli.py::test_data_search_cmd_sort_success tests/integration/test_data_cli.py::test_data_search_cmd_sort_invalid tests/integration/test_data_cli.py::test_data_search_cmd_limit[None-100] tests/integration/test_data_cli.py::test_data_search_cmd_limit[0-102] tests/integration/test_data_cli.py::test_data_search_cmd_limit[1-1] tests/integration/test_data_cli.py::test_data_search_create_filter_invalid_json[PSScene-{1:1}] tests/integration/test_data_cli.py::test_data_search_create_filter_invalid_json[PSScene-{"foo"}] tests/integration/test_data_cli.py::test_data_search_create_filter_invalid_json[SkySatScene-{1:1}] tests/integration/test_data_cli.py::test_data_search_create_filter_invalid_json[SkySatScene-{"foo"}] tests/integration/test_data_cli.py::test_data_search_create_filter_invalid_json[PSScene, tests/integration/test_data_cli.py::test_data_search_create_filter_success[PSScene] tests/integration/test_data_cli.py::test_data_search_create_filter_success[SkySatScene] tests/integration/test_data_cli.py::test_data_search_create_filter_success[PSScene, tests/integration/test_data_cli.py::test_search_create_daily_email tests/integration/test_data_cli.py::test_data_stats_invalid_filter[{1:1}] tests/integration/test_data_cli.py::test_data_stats_invalid_filter[{"foo"}] tests/integration/test_data_cli.py::test_data_stats_invalid_interval[None-1-PSScene] tests/integration/test_data_cli.py::test_data_stats_invalid_interval[None-1-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_invalid_interval[None-1-PSScene, tests/integration/test_data_cli.py::test_data_stats_invalid_interval[hou-2-PSScene] tests/integration/test_data_cli.py::test_data_stats_invalid_interval[hou-2-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_invalid_interval[hou-2-PSScene, tests/integration/test_data_cli.py::test_data_stats_invalid_interval[hour-0-PSScene] tests/integration/test_data_cli.py::test_data_stats_invalid_interval[hour-0-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_invalid_interval[hour-0-PSScene, tests/integration/test_data_cli.py::test_data_stats_success[hour-PSScene] tests/integration/test_data_cli.py::test_data_stats_success[hour-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_success[hour-PSScene, tests/integration/test_data_cli.py::test_data_stats_success[day-PSScene] tests/integration/test_data_cli.py::test_data_stats_success[day-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_success[day-PSScene, tests/integration/test_data_cli.py::test_data_stats_success[week-PSScene] tests/integration/test_data_cli.py::test_data_stats_success[week-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_success[week-PSScene, tests/integration/test_data_cli.py::test_data_stats_success[month-PSScene] tests/integration/test_data_cli.py::test_data_stats_success[month-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_success[month-PSScene, tests/integration/test_data_cli.py::test_data_stats_success[year-PSScene] tests/integration/test_data_cli.py::test_data_stats_success[year-SkySatScene] tests/integration/test_data_cli.py::test_data_stats_success[year-PSScene, tests/integration/test_data_cli.py::test_search_get tests/integration/test_data_cli.py::test_search_get_id_not_found tests/unit/test_data_item_type.py::test_item_type_success[PSScene3Band] tests/unit/test_data_item_type.py::test_item_type_success[MOD09GQ] tests/unit/test_data_item_type.py::test_item_type_success[MYD09GA] tests/unit/test_data_item_type.py::test_item_type_success[REOrthoTile] tests/unit/test_data_item_type.py::test_item_type_success[SkySatCollect] tests/unit/test_data_item_type.py::test_item_type_success[SkySatScene] tests/unit/test_data_item_type.py::test_item_type_success[MYD09GQ] tests/unit/test_data_item_type.py::test_item_type_success[Landsat8L1G] tests/unit/test_data_item_type.py::test_item_type_success[Sentinel2L1C] tests/unit/test_data_item_type.py::test_item_type_success[MOD09GA] tests/unit/test_data_item_type.py::test_item_type_success[Sentinel1] tests/unit/test_data_item_type.py::test_item_type_success[PSScene] tests/unit/test_data_item_type.py::test_item_type_success[PSOrthoTile] tests/unit/test_data_item_type.py::test_item_type_success[PSScene4Band] tests/unit/test_data_item_type.py::test_item_type_success[REScene] tests/unit/test_data_item_type.py::test_item_type_fail tests/unit/test_specs.py::test_get_type_match tests/unit/test_specs.py::test_validate_bundle_supported tests/unit/test_specs.py::test_validate_bundle_notsupported tests/unit/test_specs.py::test_validate_item_type_supported tests/unit/test_specs.py::test_validate_item_type_notsupported_bundle tests/unit/test_specs.py::test_validate_item_type_notsupported_itemtype tests/unit/test_specs.py::test_validate_order_type_supported tests/unit/test_specs.py::test_validate_order_type_notsupported tests/unit/test_specs.py::test_validate_arhive_type_supported tests/unit/test_specs.py::test_validate_arhive_type_notsupported tests/unit/test_specs.py::test_validate_file_format_supported tests/unit/test_specs.py::test_validate_file_format_notsupported tests/unit/test_specs.py::test_get_product_bundles tests/unit/test_specs.py::test_get_item_types_with_bundle tests/unit/test_specs.py::test_get_item_types_without_bundle