diff --git a/src/jaxsim/rbda/contacts/common.py b/src/jaxsim/rbda/contacts/common.py
index f87a61ca9..e6548d810 100644
--- a/src/jaxsim/rbda/contacts/common.py
+++ b/src/jaxsim/rbda/contacts/common.py
@@ -131,7 +131,7 @@ def compute_contact_forces(
         model: js.model.JaxSimModel,
         data: js.data.JaxSimModelData,
         **kwargs,
-    ) -> tuple[jtp.Vector, tuple[Any, ...]]:
+    ) -> tuple[jtp.Matrix, tuple[Any, ...]]:
         """
         Compute the contact forces.
 
@@ -140,8 +140,9 @@ def compute_contact_forces(
             data: The data of the considered model.
 
         Returns:
-            A tuple containing as first element the computed 6D contact force applied to the contact point and expressed in the world frame,
-            and as second element a tuple of optional additional information.
+            A tuple containing as first element the computed 6D contact force applied to
+            the contact points and expressed in the world frame, and as second element
+            a tuple of optional additional information.
         """
 
         pass
diff --git a/src/jaxsim/rbda/contacts/relaxed_rigid.py b/src/jaxsim/rbda/contacts/relaxed_rigid.py
index d928c1517..6770251f4 100644
--- a/src/jaxsim/rbda/contacts/relaxed_rigid.py
+++ b/src/jaxsim/rbda/contacts/relaxed_rigid.py
@@ -230,7 +230,7 @@ def compute_contact_forces(
         *,
         link_forces: jtp.MatrixLike | None = None,
         joint_force_references: jtp.VectorLike | None = None,
-    ) -> tuple[jtp.Vector, tuple[Any, ...]]:
+    ) -> tuple[jtp.Matrix, tuple]:
         """
         Compute the contact forces.
 
@@ -244,7 +244,7 @@ def compute_contact_forces(
                 Optional `(n_joints,)` vector of joint forces.
 
         Returns:
-            A tuple containing the contact forces.
+            A tuple containing as first element the computed contact forces.
         """
 
         # Initialize the model and data this contact model is operating on.
diff --git a/src/jaxsim/rbda/contacts/rigid.py b/src/jaxsim/rbda/contacts/rigid.py
index e58ac4a3a..9c99beb12 100644
--- a/src/jaxsim/rbda/contacts/rigid.py
+++ b/src/jaxsim/rbda/contacts/rigid.py
@@ -242,7 +242,7 @@ def compute_contact_forces(
         *,
         link_forces: jtp.MatrixLike | None = None,
         joint_force_references: jtp.VectorLike | None = None,
-    ) -> tuple[jtp.Vector, tuple[Any, ...]]:
+    ) -> tuple[jtp.Matrix, tuple]:
         """
         Compute the contact forces.
 
@@ -256,7 +256,7 @@ def compute_contact_forces(
                 Optional `(n_joints,)` vector of joint forces.
 
         Returns:
-            A tuple containing the contact forces.
+            A tuple containing as first element the computed contact forces.
         """
 
         # Initialize the model and data this contact model is operating on.
diff --git a/src/jaxsim/rbda/contacts/soft.py b/src/jaxsim/rbda/contacts/soft.py
index 8b626bc00..4af693527 100644
--- a/src/jaxsim/rbda/contacts/soft.py
+++ b/src/jaxsim/rbda/contacts/soft.py
@@ -423,7 +423,18 @@ def compute_contact_forces(
         self,
         model: js.model.JaxSimModel,
         data: js.data.JaxSimModelData,
-    ) -> tuple[jtp.Vector, tuple[jtp.Vector]]:
+    ) -> tuple[jtp.Matrix, tuple[jtp.Matrix]]:
+        """
+        Compute the contact forces.
+
+        Args:
+            model: The model to consider.
+            data: The data of the considered model.
+
+        Returns:
+            A tuple containing as first element the computed contact forces, and as
+            second element the derivative of the material deformation.
+        """
 
         # Initialize the model and data this contact model is operating on.
         # This will raise an exception if either the contact model or the
diff --git a/src/jaxsim/rbda/contacts/visco_elastic.py b/src/jaxsim/rbda/contacts/visco_elastic.py
index 35e7342a5..dcbfd3d20 100644
--- a/src/jaxsim/rbda/contacts/visco_elastic.py
+++ b/src/jaxsim/rbda/contacts/visco_elastic.py
@@ -266,7 +266,7 @@ def compute_contact_forces(
         dt: jtp.FloatLike,
         link_forces: jtp.MatrixLike | None = None,
         joint_force_references: jtp.VectorLike | None = None,
-    ) -> tuple[jtp.Vector, tuple[Any, ...]]:
+    ) -> tuple[jtp.Matrix, tuple[jtp.Matrix, jtp.Matrix]]:
         """
         Compute the contact forces.