diff --git a/pyvo/registry/rtcons.py b/pyvo/registry/rtcons.py
index 914fde9d..301a18b0 100644
--- a/pyvo/registry/rtcons.py
+++ b/pyvo/registry/rtcons.py
@@ -241,7 +241,7 @@ def get_search_condition(self, service):
 
 class Freetext(Constraint):
     """
-    A contraint using plain text to match against title, description,
+    A constraint using plain text to match against title, description,
     subjects, and person names.
     """
     _keyword = "keywords"
@@ -251,11 +251,17 @@ def __init__(self, *words: str):
 
         Parameters
         ----------
-        *words : tuple of str
+        *words : str
+            One or more string arguments.
             It is recommended to pass multiple words in multiple strings
             arguments.  You can pass in phrases (i.e., multiple words
             separated by space), but behaviour might then vary quite
             significantly between different registries.
+
+        Examples
+        --------
+        >>> from pyvo import registry
+        >>> registry.Freetext("Gamma", "Ray", "Burst") # doctest: +IGNORE_OUTPUT
         """
         self.words = words
 
@@ -387,7 +393,7 @@ def __init__(self, *stds):
 
         Parameters
         ----------
-        *stds : tuple of str
+        *stds : str
             one or more standards identifiers.  The constraint will
             match records that have any of them.
         """
@@ -462,7 +468,7 @@ def __init__(self, *bands):
 
         Parameters
         ----------
-        *bands : tuple of strings
+        *bands : strings
             One or more of the terms given in http://www.ivoa.net/rdf/messenger.
             The constraint matches when a resource declares at least
             one of the messengers listed.
@@ -559,6 +565,7 @@ def __init__(self, ivoid, *more_ivoids):
         ----------
 
         ivoid : string
+            One or more string arguments.
             The IVOA identifier of the resource to match.  As RegTAP
             requires lowercasing ivoids on ingestion, the constraint
             lowercases the ivoid passed in, too.
@@ -588,7 +595,7 @@ def __init__(self, *patterns):
         Parameters
         ----------
 
-        patterns : tuple of strings
+        patterns : strings
             SQL patterns (i.e., ``%`` is 0 or more characters) for
             UCDs.  The constraint will match when a resource has
             at least one column matching one of the patterns.