diff --git a/model/src/pyrenew/process/ar.py b/model/src/pyrenew/process/ar.py
index 9ce5e941..16a29568 100644
--- a/model/src/pyrenew/process/ar.py
+++ b/model/src/pyrenew/process/ar.py
@@ -58,7 +58,8 @@ def sample(
         name : str, optional
             Name of the parameter passed to numpyro.sample.
         **kwargs : dict, optional
-            Ignored.
+            Additional keyword arguments passed through to internal sample()
+            calls, should there be any.
 
         Returns
         -------
@@ -85,4 +86,7 @@ def _ar_scanner(carry, next):
 
     @staticmethod
     def validate():
+        """
+        Validates inputted parameters, implementation pending.
+        """
         return None
diff --git a/model/src/pyrenew/process/firstdifferencear.py b/model/src/pyrenew/process/firstdifferencear.py
index 7f94b966..84d32edb 100644
--- a/model/src/pyrenew/process/firstdifferencear.py
+++ b/model/src/pyrenew/process/firstdifferencear.py
@@ -54,7 +54,8 @@ def sample(
         name : str, optional
             Passed to ARProcess.sample(), by default "trend_rw"
         **kwargs : dict, optional
-            Ignored.
+            Additional keyword arguments passed through to internal sample()
+            calls, should there be any.
 
         Returns
         -------
@@ -67,4 +68,7 @@ def sample(
 
     @staticmethod
     def validate():
+        """
+        Validates inputted parameters, implementation pending.
+        """
         return None
diff --git a/model/src/pyrenew/process/rtrandomwalk.py b/model/src/pyrenew/process/rtrandomwalk.py
index bff8a460..c6cb32c9 100644
--- a/model/src/pyrenew/process/rtrandomwalk.py
+++ b/model/src/pyrenew/process/rtrandomwalk.py
@@ -23,7 +23,7 @@ def __init__(
         Parameters
         ----------
         Rt0_dist : dist.Distribution, optional
-            Initial distributiono of Rt, defaults to
+            Initial distribution of Rt, defaults to
             dist.TruncatedNormal( loc=1.2, scale=0.2, low=0 )
         Rt_transform : AbstractTransform, optional
             Transformation applied to the sampled Rt0, defaults
@@ -44,7 +44,35 @@ def __init__(
         return None
 
     @staticmethod
-    def validate(Rt0_dist, Rt_transform, Rt_rw_dist):
+    def validate(
+        Rt0_dist: dist.Distribution,
+        Rt_transform: AbstractTransform,
+        Rt_rw_dist: dist.Distribution,
+    ) -> None:
+        """
+        Validates Rt0_dist, Rt_transform, and Rt_rw_dist.
+
+        Parameters
+        ----------
+        Rt0_dist : dist.Distribution, optional
+            Initial distribution of Rt, expected dist.Distribution
+        Rt_transform : any
+            Transformation applied to the sampled Rt0, expected
+            AbstractTransform
+        Rt_rw_dist : any
+            Randomwalk process, expected dist.Distribution.
+
+        Returns
+        -------
+        None
+
+        Raises
+        ------
+        AssertionError
+            If Rt0_dist or Rt_rw_dist are not dist.Distribution or if
+            Rt_transform is not AbstractTransform.
+
+        """
         assert isinstance(Rt0_dist, dist.Distribution)
         assert isinstance(Rt_transform, AbstractTransform)
         assert isinstance(Rt_rw_dist, dist.Distribution)
@@ -61,7 +89,8 @@ def sample(
         n_timepoints : int
             Number of timepoints to sample.
         **kwargs : dict, optional
-            Ignored.
+            Additional keyword arguments passed through to internal sample()
+            calls, should there be any.
 
         Returns
         -------
diff --git a/model/src/pyrenew/process/simplerandomwalk.py b/model/src/pyrenew/process/simplerandomwalk.py
index f395212a..59e37973 100644
--- a/model/src/pyrenew/process/simplerandomwalk.py
+++ b/model/src/pyrenew/process/simplerandomwalk.py
@@ -48,7 +48,8 @@ def sample(
         init : float, optional
             Initial point of the walk, by default None
         **kwargs : dict, optional
-            Ignored.
+            Additional keyword arguments passed through to internal sample()
+            calls, should there be any.
 
         Returns
         -------
@@ -65,4 +66,7 @@ def sample(
 
     @staticmethod
     def validate():
+        """
+        Validates inputted parameters, implementation pending.
+        """
         return None