diff --git a/python/cudf_polars/cudf_polars/containers/dataframe.py b/python/cudf_polars/cudf_polars/containers/dataframe.py
index 2ed4298e993..2a4ad60b051 100644
--- a/python/cudf_polars/cudf_polars/containers/dataframe.py
+++ b/python/cudf_polars/cudf_polars/containers/dataframe.py
@@ -37,6 +37,8 @@ class DataFrame:
     def __init__(self, columns: Sequence[Column], scalars: Sequence[Scalar]) -> None:
         self.columns = list(columns)
         self._column_map = {c.name: c for c in self.columns}
+        if len(self._column_map) != len(self.columns):
+            raise ValueError("Some columns have overlapping names")
         self.scalars = list(scalars)
         if len(scalars) == 0:
             self.table = plc.Table([c.obj for c in columns])
@@ -89,7 +91,25 @@ def from_cudf(cls, df: cudf.DataFrame) -> Self:
 
     @classmethod
     def from_table(cls, table: plc.Table, names: Sequence[str]) -> Self:
-        """Create from a pylibcudf table."""
+        """
+        Create from a pylibcudf table.
+
+        Parameters
+        ----------
+        table
+            Pylibcudf table to obtain columns from
+        names
+            Names for the columns
+
+        Returns
+        -------
+        New dataframe sharing  data with the input table.
+
+        Raises
+        ------
+        ValueError if the number of provided names does not match the
+        number of columns in the table.
+        """
         # TODO: strict=True when we drop py39
         if table.num_columns() != len(names):
             raise ValueError("Mismatching name and table length.")
@@ -98,7 +118,24 @@ def from_table(cls, table: plc.Table, names: Sequence[str]) -> Self:
     def sorted_like(
         self, like: DataFrame, /, *, subset: Set[str] | None = None
     ) -> Self:
-        """Copy sortedness from a dataframe onto self."""
+        """
+        Copy sortedness from a dataframe onto self.
+
+        Parameters
+        ----------
+        like
+            The dataframe to copy from
+        subset
+            Optional subset of columns from which to copy data.
+
+        Returns
+        -------
+        Self with metadata set.
+
+        Raises
+        ------
+        ValueError if there is a name mismatch between self and like.
+        """
         if like.column_names != self.column_names:
             raise ValueError("Can only copy from identically named frame")
         subset = self.column_names_set if subset is None else subset
@@ -112,7 +149,19 @@ def with_columns(self, columns: Sequence[Column]) -> Self:
         """
         Return a new dataframe with extra columns.
 
-        Data is shared.
+        Parameters
+        ----------
+        columns
+            Columns to add
+
+        Returns
+        -------
+        New dataframe
+
+        Raises
+        ------
+        ValueError if the new columns have overlapping names with the
+        existing ones.
         """
         return type(self)([*self.columns, *columns], self.scalars)
 
diff --git a/python/cudf_polars/cudf_polars/dsl/expr.py b/python/cudf_polars/cudf_polars/dsl/expr.py
index d96a6464404..249cc3775f7 100644
--- a/python/cudf_polars/cudf_polars/dsl/expr.py
+++ b/python/cudf_polars/cudf_polars/dsl/expr.py
@@ -183,12 +183,21 @@ def do_evaluate(
         Notes
         -----
         Do not call this function directly, but rather
-        :func:`evaluate` which handles the mapping lookups.
+        :meth:`evaluate` which handles the mapping lookups.
+
+        The typed return value of :class:`Column` is not true when
+        evaluating :class:`Literal` nodes (which instead produce
+        :class:`Scalar` objects). However, these duck-type to having a
+        pylibcudf container object inside them, and usually they end
+        up appearing in binary expressions which pylibcudf handles
+        appropriately since there are overloads for (column, scalar)
+        pairs. We don't have to handle (scalar, scalar) in binops
+        since the polars optimizer has a constant-folding pass.
 
         Returns
         -------
         Column representing the evaluation of the expression (or maybe
-        a scalar, annoying!).
+        a scalar).
 
         Raises
         ------