diff --git a/docs/internals.rst b/docs/internals.rst
index 7d607bfe..f1064b8b 100644
--- a/docs/internals.rst
+++ b/docs/internals.rst
@@ -903,6 +903,113 @@ Adds a new metadata entry for the specified column.
 Any previous column-level metadata entry with the same ``key`` will be overwritten.
 Internally upserts the value into the  the ``metadata_columns`` table inside the :ref:`internal database <internals_internal>`.
 
+.. _datasette_column_types:
+
+Column types
+------------
+
+Column types are stored in the ``column_types`` table in the :ref:`internal database <internals_internal>`. The following methods provide the API for reading and modifying column type assignments.
+
+.. _datasette_get_column_type:
+
+await .get_column_type(database, resource, column)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``database`` - string
+    The name of the database.
+``resource`` - string
+    The name of the table or view.
+``column`` - string
+    The name of the column.
+
+Returns a ``(column_type_name, config)`` tuple for the specified column. ``column_type_name`` is a string like ``"email"`` or ``"url"``, and ``config`` is a dict or ``None``. If no column type is assigned, returns ``(None, None)``.
+
+.. code-block:: python
+
+    ct_name, config = await datasette.get_column_type(
+        "mydb", "mytable", "email_col"
+    )
+
+.. _datasette_get_column_types:
+
+await .get_column_types(database, resource)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``database`` - string
+    The name of the database.
+``resource`` - string
+    The name of the table or view.
+
+Returns a dictionary mapping column names to ``(column_type_name, config)`` tuples for all columns that have assigned types on the given resource.
+
+.. code-block:: python
+
+    ct_map = await datasette.get_column_types(
+        "mydb", "mytable"
+    )
+    # {"email_col": ("email", None), "site": ("url", None)}
+
+.. _datasette_set_column_type:
+
+await .set_column_type(database, resource, column, column_type, config=None)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``database`` - string
+    The name of the database.
+``resource`` - string
+    The name of the table or view.
+``column`` - string
+    The name of the column.
+``column_type`` - string
+    The column type name to assign, e.g. ``"email"``.
+``config`` - dict, optional
+    Optional configuration dict for the column type.
+
+Assigns a column type to a column. Overwrites any existing assignment for that column.
+
+.. code-block:: python
+
+    await datasette.set_column_type(
+        "mydb", "mytable", "location", "point",
+        config={"srid": 4326}
+    )
+
+.. _datasette_remove_column_type:
+
+await .remove_column_type(database, resource, column)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``database`` - string
+    The name of the database.
+``resource`` - string
+    The name of the table or view.
+``column`` - string
+    The name of the column.
+
+Removes the column type assignment for the specified column.
+
+.. code-block:: python
+
+    await datasette.remove_column_type(
+        "mydb", "mytable", "location"
+    )
+
+.. _datasette_get_column_type_class:
+
+.get_column_type_class(column_type_name)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+``column_type_name`` - string
+    The name of the column type, e.g. ``"email"``.
+
+Returns the registered ``ColumnType`` instance for the given name, or ``None`` if no plugin has registered a column type with that name. This is a synchronous method.
+
+.. code-block:: python
+
+    ct = datasette.get_column_type_class("email")
+    if ct:
+        print(ct.description)  # "Email address"
+
 .. _datasette_add_database:
 
 .add_database(db, name=None, route=None)