diff --git a/pymc/distributions/continuous.py b/pymc/distributions/continuous.py
index 1d30227fe..85e1f695b 100644
--- a/pymc/distributions/continuous.py
+++ b/pymc/distributions/continuous.py
@@ -214,8 +214,10 @@ def get_tau_sigma(
 
     Parameters
     ----------
-    tau: array-like, optional
-    sigma: array-like, optional
+    tau : array-like, optional
+        Precision (tau > 0) (required if sigma is not specified)
+    sigma : array-like, optional
+        Standard deviation (sigma > 0) (required if tau is not specified)
 
     Results
     -------