diff --git a/README.rst b/README.rst
index b733c64..64063bd 100644
--- a/README.rst
+++ b/README.rst
@@ -25,7 +25,7 @@ Script to create citation file formatted file (https://citation-file-format.gith
 
 Current supported DOI types:
 
-* Zenodo software from a GitHub release (https://guides.github.com/activities/citable-code/)
+* Zenodo upload from a GitHub release (https://guides.github.com/activities/citable-code/)
 
 Free software: Apache Software License 2.0
 
diff --git a/doi2cff/cli.py b/doi2cff/cli.py
index 654d924..cd4ac34 100644
--- a/doi2cff/cli.py
+++ b/doi2cff/cli.py
@@ -19,7 +19,7 @@ def main():
 
     Current supported DOI types:
 
-        * Zenodo software from a GitHub release (https://guides.github.com/activities/citable-code/)
+        * Zenodo upload of a GitHub release (https://guides.github.com/activities/citable-code/)
 
     """
     pass
@@ -39,7 +39,7 @@ def is_software_zenodo(zenodo_record):
 def init(doi, cff_fn):
     """Generate CITATION.cff file based on a Zenodo DOI of a Github release.
 
-    * DOI, The Zenodo DOI url of a GitHub release
+    * DOI, The Digital Object Identifier (DOI) name of a Zenodo upload of a GitHub release
     """
     template = '''# YAML 1.2
 # Metadata for citation of this software according to the CFF format (https://citation-file-format.github.io/)
@@ -57,12 +57,12 @@ def init(doi, cff_fn):
     '''
 
     if not doi_is_from_zenodo(doi):
-        raise NotImplemented('Unable to process doi, converter not implemented')
+        raise click.UsageError('Unable to process DOI name, only accept DOI name which is a Zenodo upload')
 
     zenodo_record = fetch_zenodo_by_doiurl(doi)
 
     if not is_software_zenodo(zenodo_record):
-        raise NotImplemented('Unable to process doi, converter not implemented for Zenodo entries other than software')
+        raise click.UsageError('Unable to process DOI name, only accept DOI name which is a Zenodo upload of type software')
 
     yaml = ruamel.yaml.YAML()
     data = yaml.load(template)
@@ -101,7 +101,7 @@ def init(doi, cff_fn):
 def update(doi, cff_fn):
     """Update CITATION.cff with doi, version and release date of a new release
 
-    * DOI, The Zenodo DOI url of a GitHub release
+    * DOI, The Digital Object Identifier (DOI) name of a Zenodo upload of a GitHub release
     """
     update_version(doi, cff_fn)
 
@@ -129,9 +129,9 @@ def tagurl_of_zenodo(record):
         if related_identifier['relation'] == 'isSupplementTo':
 
             return related_identifier['identifier']
-    msg = 'Unable to process DOI, Zenodo record does not contain a related identifier ' \
+    msg = 'Unable to process DOI name, Zenodo upload does not contain a related identifier ' \
           'with isSupplementTo relation, which is expected for DOI generated by GitHub'
-    raise KeyError(msg)
+    raise click.UsageError(msg)
 
 
 def tagurl2repo(tagurl):
@@ -228,7 +228,7 @@ def authors_of_csl(record):
                 'family-names': name.last,
             }
         else:
-            raise NotImplemented('Do not understand author field: {}'.format(a))
+            raise click.UsageError('Unable to process DOI name, do not understand author field: {}'.format(a))
         authors.append(author)
     return authors