diff --git a/devtools/envs/base.yaml b/devtools/envs/base.yaml
index 13a49d9..0524403 100644
--- a/devtools/envs/base.yaml
+++ b/devtools/envs/base.yaml
@@ -53,7 +53,7 @@ dependencies:
   - codecov
 
   # Docs
-  - mkdocs
+  - mkdocs <1.6
   - mkdocs-material
   - mkdocs-gen-files
   - mkdocs-literate-nav
diff --git a/smee/_models.py b/smee/_models.py
index 668a9d9..3c762e3 100644
--- a/smee/_models.py
+++ b/smee/_models.py
@@ -164,6 +164,19 @@ class TensorTopology:
     """Distance constraints that should be applied **during MD simulations**. These
     will not be used outside of MD simulations."""
 
+    residue_idxs: list[int] | None = None
+    """The index of the residue that each atom in the topology belongs to with
+    ``length=n_atoms``."""
+    residue_ids: list[str] | None = None
+    """The names of the residues that each atom belongs to with ``length=n_residues``.
+    """
+
+    chain_idxs: list[int] | None = None
+    """The index of the chain that each atom in the topology belongs to with
+    ``length=n_atoms``."""
+    chain_ids: list[str] | None = None
+    """The names of the chains that each atom belongs to with ``length=n_chains``."""
+
     @property
     def n_atoms(self) -> int:
         """The number of atoms in the topology."""
@@ -174,6 +187,16 @@ def n_bonds(self) -> int:
         """The number of bonds in the topology."""
         return len(self.bond_idxs)
 
+    @property
+    def n_residues(self) -> int:
+        """The number of residues in the topology"""
+        return 0 if self.residue_ids is None else len(self.residue_ids)
+
+    @property
+    def n_chains(self) -> int:
+        """The number of chains in the topology"""
+        return 0 if self.chain_ids is None else len(self.chain_ids)
+
     @property
     def n_v_sites(self) -> int:
         """The number of v-sites in the topology."""
@@ -200,6 +223,9 @@ def to(
                 if self.constraints is None
                 else self.constraints.to(device, precision)
             ),
+            self.residue_idxs,
+            self.residue_ids,
+            self.chain_ids,
         )
 
 
diff --git a/smee/tests/test_models.py b/smee/tests/test_models.py
index 82e1097..791a3f9 100644
--- a/smee/tests/test_models.py
+++ b/smee/tests/test_models.py
@@ -54,6 +54,24 @@ def test_n_bonds(self):
         expected_n_bonds = 5
         assert topology.n_bonds == expected_n_bonds
 
+    def test_n_residues(self):
+        topology = smee.tests.utils.topology_from_smiles("[Ar]")
+        topology.residue_ids = None
+        topology.residue_idxs = None
+        assert topology.n_residues == 0
+
+        topology.residue_ids = ["Ar"]
+        topology.residue_idxs = [0]
+        assert topology.n_residues == 1
+
+    def test_n_chains(self) -> int:
+        topology = smee.tests.utils.topology_from_smiles("[Ar]")
+        topology.residue_ids = [0]
+        topology.residue_idxs = ["UNK"]
+        topology.chain_idxs = [0]
+        topology.chain_ids = ["A"]
+        assert topology.n_chains == 1
+
     def test_n_v_sites(self):
         topology = smee.tests.utils.topology_from_smiles("CO")