diff --git a/grace/generators/model_generator.py b/grace/generators/model_generator.py
index 39e7400..a39cb33 100644
--- a/grace/generators/model_generator.py
+++ b/grace/generators/model_generator.py
@@ -4,9 +4,21 @@
 from click.core import Argument
 from jinja2_strcase.jinja2_strcase import to_snake
 
+from grace.exceptions import ValidationError
 from grace.generator import Generator
 from grace.generators.migration_generator import generate_migration
 
+# Field annotations must be plain Python types Pydantic can build a schema for,
+# not SQLAlchemy column type classes (e.g. `str`, not `String`) - see
+# https://docs.pydantic.dev/latest/concepts/types/ for what's supported.
+COLUMN_TYPES: dict[str, str] = {
+    "String": "str",
+    "Text": "str",
+    "Integer": "int",
+    "Float": "float",
+    "Boolean": "bool",
+}
+
 
 class ModelGenerator(Generator):
     NAME: str = "model"
@@ -24,9 +36,7 @@ def generate(self, name: str, params: tuple[str]):
         a SQLAlchemy-style definition. You can specify column names and types
         during generation using the format `column_name:Type`.
 
-        Supported types are any valid SQLAlchemy column types
-        (e.g., `String`, `Integer`, `Boolean`, etc.).
-        See https://docs.sqlalchemy.org/en/20/core/types.html
+        Supported types: String, Text, Integer, Float, Boolean.
 
         Example:
         ```bash
@@ -80,12 +90,20 @@ def extract_columns(self, params: tuple[str]) -> tuple[list, list]:
         types = []
 
         for param in params:
-            name, type = param.split(":")
+            name, type_ = param.split(":")
+
+            if type_ not in COLUMN_TYPES:
+                raise ValidationError(
+                    f"Unsupported column type '{type_}' for '{name}'. "
+                    f"Supported types: {', '.join(sorted(COLUMN_TYPES))}."
+                )
+
+            python_type = COLUMN_TYPES[type_]
 
-            if type not in types:
-                types.append(type)
+            if python_type not in types:
+                types.append(python_type)
 
-            columns.append((name, type))
+            columns.append((name, python_type))
 
         return columns, types
 
diff --git a/tests/generators/test_model_generator.py b/tests/generators/test_model_generator.py
index fbd3588..4b67afc 100644
--- a/tests/generators/test_model_generator.py
+++ b/tests/generators/test_model_generator.py
@@ -2,6 +2,7 @@
 
 import pytest
 
+from grace.exceptions import ValidationError
 from grace.generator import Generator
 from grace.generators.model_generator import ModelGenerator
 
@@ -13,6 +14,18 @@ def generator():
     return generator
 
 
+def test_extract_columns_with_supported_types__expect_python_annotations(generator):
+    columns, types = generator.extract_columns(("message:String", "age:Integer"))
+
+    assert columns == [("message", "str"), ("age", "int")]
+    assert types == ["str", "int"]
+
+
+def test_extract_columns_with_unsupported_type__expect_validation_error(generator):
+    with pytest.raises(ValidationError, match="Unsupported column type 'DateTime'"):
+        generator.extract_columns(("created_at:DateTime",))
+
+
 def test_generate_without_app__expect_value_error(generator):
     generator.app = None
 
@@ -32,15 +45,32 @@ def test_generate_without_database__expect_no_file_and_warning(
     assert "no database configured" in caplog.text.lower()
 
 
-def test_generate_with_database__expect_model_file_and_migration_generated(
-    mocker, generator
-):
+def test_generate__expect_model_file_with_python_type_annotations(mocker, generator):
     mock_generate_file = mocker.patch.object(Generator, "generate_file")
+    mocker.patch("grace.generators.model_generator.generate_migration")
+
+    generator.generate("Greeting", ("message:String",))
+
+    mock_generate_file.assert_called_once()
+    variables = mock_generate_file.call_args.kwargs["variables"]
+    assert list(variables["model_columns"]) == ["message: str"]
+    assert variables["model_column_types"] == ["str"]
+
+
+def test_generate__expect_migration_generated(mocker, generator):
+    mocker.patch.object(Generator, "generate_file")
     mock_generate_migration = mocker.patch(
         "grace.generators.model_generator.generate_migration"
     )
 
     generator.generate("Greeting", ("message:String",))
 
-    mock_generate_file.assert_called_once()
     mock_generate_migration.assert_called_once_with(generator.app, "Create Greeting")
+
+
+def test_validate_valid_name__expect_true(generator):
+    assert generator.validate("Greeting")
+
+
+def test_validate_invalid_name__expect_false(generator):
+    assert not generator.validate("greeting")