diff --git a/docs/style.css b/docs/style.css
new file mode 100644
index 0000000..f8ae9a9
--- /dev/null
+++ b/docs/style.css
@@ -0,0 +1,190 @@
+body {
+    color: #333;
+    background-color: #f2f2f2;
+    font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
+    padding: 1em 5em;
+}
+
+h1,h2,h3,h4,h5,h6,th {
+    font-family: 'Archivo Black', Helvetica, Arial, sans-serif;
+}
+
+th,td {
+    border: thin solid darkgray;
+    padding: 0.25em 1em;
+    text-align: left;
+    vertical-align: top;
+}
+
+th {
+    background-color: silver;
+}
+
+.container {
+    max-width: 1000px;
+}
+
+.right {
+    float: right;
+    text-align: right;
+}
+
+.navbar {
+    border-radius: 0;
+    box-shadow: 0 0 0 0, 0 6px 12px rgba(34, 34, 34, 0.3);
+}
+
+.navbar-default {
+    background-color: #002b00;
+    border: none;
+}
+
+.navbar-default .navbar-brand {
+    color: #fff;
+    font-family: 'Archivo Black', Helvetica, Arial, sans-serif;
+}
+
+.navbar-default .navbar-brand:hover {
+    color: #fff;
+}
+
+.navbar-default .navbar-nav li a {
+    color: #fff;
+}
+
+.navbar-default .navbar-nav li a:hover {
+    color: #fff;
+    background-color: #002b00;
+}
+
+.navbar-default .navbar-nav .active a {
+    color: #fff;
+    background-color: #002b00;
+}
+
+.navbar-default .navbar-toggle:hover {
+    background-color: #002b00;
+}
+
+.navbar-default .navbar-toggle .icon-bar {
+    background-color: #fff;
+}
+
+#sidebar {
+    margin-left: 15px;
+    margin-top: 50px;
+}
+
+#content {
+    background-color: #fff;
+    border-radius: 3px;
+    box-shadow: 0 0 0 0, 0 6px 12px rgba(34, 34, 34, 0.1);
+}
+
+#content img {
+    max-width: 100%;
+    height: auto;
+}
+
+footer {
+    font-size: 14px;
+    text-align: center;
+    padding-top: 75px;
+    padding-bottom: 30px;
+}
+
+blockquote footer {
+    text-align: left;
+    padding-top: 0px;
+    padding-bottom: 0px;
+}
+
+#post-tags {
+    margin-top: 30px;
+}
+
+#prev-next {
+    padding: 15px 0;
+}
+
+.post-header {
+    margin-bottom: 20px;
+}
+
+.post-header h2 {
+    font-size: 32px;
+}
+
+#post-meta {
+    font-size: 14px;
+    color: rgba(0, 0, 0, 0.4)
+}
+
+#page-header {
+    border-bottom: 1px solid #dbdbdb;
+    margin-bottom: 20px;
+}
+
+#page-header h2 {
+    font-size: 32px;
+}
+
+pre {
+    overflow-x: auto;
+}
+
+pre code {
+    display: block;
+    padding: 0.5em;
+    overflow-wrap: normal;
+    white-space: pre;
+}
+
+code {
+    color: #002b00;
+}
+
+pre,
+code,
+.hljs {
+    background-color: #f7f9fd;
+}
+
+@media (min-width: 768px) {
+    .navbar {
+        min-height: 70px;
+    }
+
+    .navbar-nav>li>a {
+        padding: 30px 20px;
+    }
+
+    .navbar-default .navbar-brand {
+        font-size: 36px;
+        padding: 25px 15px;
+    }
+
+    #content {
+        margin-top: 30px;
+        padding: 30px 40px;
+    }
+}
+
+@media (max-width: 767px) {
+    body {
+        font-size: 14px;
+    }
+
+    .navbar-default .navbar-brand {
+        font-size: 30px;
+    }
+
+    #content {
+        padding: 15px;
+    }
+
+    #post-meta .right {
+        float: left;
+        text-align: left;
+    }
+}
\ No newline at end of file
diff --git a/project.clj b/project.clj
index 94244ed..5b4db8d 100644
--- a/project.clj
+++ b/project.clj
@@ -10,16 +10,21 @@
   :dependencies [[clj-activitypub/activitypub "0.52"]
                  [clojure.java-time "1.1.0"]
                  [com.taoensso/timbre "6.0.4"]
+                 [hiccup "1.0.5"]
                  [mvxcvi/clj-pgp "1.1.0"]
                  [org.bouncycastle/bcpkix-jdk18on "1.72"] 
-                 [org.clojars.simon_brooke/internationalisation "1.0.4"]
+                 [org.clojars.simon_brooke/internationalisation "1.0.5"]
                  [org.clojure/clojure "1.11.1"]
                  [org.clojure/data.json "2.4.0"]
                  [org.clojure/math.numeric-tower "0.0.5"]
-                 [org.clojure/spec.alpha "0.3.218"]]
+                 [org.clojure/spec.alpha "0.3.218"]
+                 [org.clojure/tools.cli "1.0.214"]
+                 [trptr/java-wrapper "0.2.3"]]
   :license {:name "GPL-2.0-or-later"
             :url "https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html"}
+  :main dog-and-duck.quack.cli
   :plugins [[lein-cloverage "1.2.2"]
             [lein-codox "0.10.7"]]
-  :repl-options {:init-ns dog-and-duck.scratch.core}
+  :profiles {:uberjar {:aot :all}}
+  :repl-options {:init-ns dog-and-duck.quack.cli}
   :url "http://example.com/FIXME")
diff --git a/resources/i18n/en-GB.edn b/resources/i18n/en-GB.edn
index d751dfa..09e0afd 100644
--- a/resources/i18n/en-GB.edn
+++ b/resources/i18n/en-GB.edn
@@ -15,10 +15,13 @@
 ;;;     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
 ;; Actual fault messages to which fault codes resolve: English language version.
-{:expected-collection "A collection was expected, but was not found."
+{:by "by"
+ :expected-collection "A collection was expected, but was not found."
+ :generated-on "Generated on"
  :id-not-https "Publicly facing content SHOULD use HTTPS URIs"
  :id-not-uri "identifiers must be publicly dereferencable URIs"
  :no-context "Section 3 of the ActivityPub specification states Implementers SHOULD include the ActivityPub context in their object definitions`."
+ :no-faults-found "No faults were found."
  :no-id-persistent "Persistent objects MUST have unique global identifiers."
  :no-id-transient "The ActivityPub specification allows objects without `id` fields only if they are intentionally transient; even so it is preferred that the object should have an explicit null id."
  :no-inbox "Actor objects MUST have an `inbox` property, whose value MUST be a reference to an ordered collection."
@@ -28,4 +31,5 @@
  :not-actor-type "The `type` value of the object was not a recognised actor type."
  :not-valid-date-time "A date/time of format required for `xsd:dateTime` was expected but was not found."
  :null-id-persistent "Persistent objects MUST have non-null identifiers."
- :not-an-object "ActivityStreams object must be JSON objects."}
\ No newline at end of file
+ :not-an-object "ActivityStreams object must be JSON objects."
+ :validation-report-for "Validation report for"}
\ No newline at end of file
diff --git a/src/dog_and_duck/activitypub.code-workspace b/src/dog_and_duck/activitypub.code-workspace
index b1e3e48..ec57959 100644
--- a/src/dog_and_duck/activitypub.code-workspace
+++ b/src/dog_and_duck/activitypub.code-workspace
@@ -5,6 +5,9 @@
 		},
 		{
 			"path": "../../../clj-activitypub"
+		},
+		{
+			"path": "../../../internationalisation"
 		}
 	],
 	"settings": {}
diff --git a/src/dog_and_duck/quack/cli.clj b/src/dog_and_duck/quack/cli.clj
new file mode 100644
index 0000000..3abb365
--- /dev/null
+++ b/src/dog_and_duck/quack/cli.clj
@@ -0,0 +1,139 @@
+(ns dog-and-duck.quack.cli
+  (:require [clojure.data.json :refer [read-str]]
+            [clojure.java.io :refer [resource]]
+            [clojure.pprint :refer [pprint]]
+            [clojure.string :refer [join]]
+            [clojure.tools.cli :refer [parse-opts]]
+            [clojure.walk :refer [keywordize-keys]]
+            [dog-and-duck.quack.picky.constants :refer [severity]]
+            [dog-and-duck.quack.picky.objects :refer [object-faults]]
+            [dog-and-duck.quack.picky.utils :refer [filter-severity]]
+            [hiccup.core :refer [html]]
+            [scot.weft.i18n.core :refer [get-message *config*]]
+            [trptr.java-wrapper.locale :as locale])
+  (:gen-class))
+
+(def ^:const stylesheet-url
+  ;; TODO: fix this to github pages before go live
+  "https://simon-brooke.github.io/dog-and-duck/style.css")
+
+(def cli-options
+  ;; An option with a required argument
+  [["-i" "--input SOURCE" "The file or URL to validate"
+    :default "standard input"]
+   ["-o" "--output DEST" "The file to write to, defaults to standard out"
+    :default "standard output"]
+   ["-f" "--format FORMAT" "The format to output, one of `edn` `csv` `html`"
+    :default :edn
+    :parse-fn #(keyword %)
+    :validate [#(#{:csv :edn :html} %) "Expect one of `edn` `csv` `html`"]]
+   ["-l" "--language LANG" "The ISO 639-1 language code for the language to output"
+    :default (-> (locale/get-default) locale/to-language-tag)]
+   ["-s" "--severity LEVEL" "The minimum severity of faults to report"
+    :default :info
+    :parse-fn #(keyword %)
+    :validate [#(severity %) (join " "
+                                   (cons
+                                    "Expected one of"
+                                    (map name severity)))]]
+   ["-h" "--help"]])
+
+(defn validate
+  [source]
+  (println (str "Reading " source))
+  (let [input (read-str (slurp source))]
+    (cond (map? input) (object-faults (keywordize-keys input))
+          (and (coll? input)
+               (every? map? input)) (map #(object-faults
+                                           (keywordize-keys %)
+                                           input)))))
+
+(defn output-csv
+  [faults]
+  (let [cols (set (reduce concat (map keys faults)))]
+    (with-out-str
+      (println (join ", " (map name cols)))
+      (map
+       #(println (join ", " (map (fn [p] (p %)) cols)))
+       faults))))
+
+(defn html-header-row
+  [cols]
+  (apply vector (cons :tr (map #(vector :th (name %)) cols))))
+
+(defn html-fault-row
+  [fault cols]
+  (apply
+   vector (cons :tr (map (fn [col] (vector :td (col fault))) cols))))
+
+(defn- version-string []
+  (join
+   " "
+   ["dog-and-duck/quack"
+    (try
+      (some->>
+       (resource "META-INF/maven/dog-and-duck/dog-and-duck/pom.properties")
+       slurp
+       (re-find #"version=(.*)")
+       second)
+      (catch Exception _ nil))]))
+
+(defn output-html
+  [faults opts]
+  (let [source-name (if (= (:input opts) *in*) "Standard input" (str (:input opts)))
+        title (join " " [(get-message :validation-report-for) source-name])
+        cols (set (reduce concat (map keys faults)))
+        version (version-string)]
+    (str
+     "<!DOCTYPE html>"
+     (html
+      [:html
+       [:head
+        [:title title]
+        [:meta {:name "generator" :content version}]
+        [:link {:rel "stylesheet" :media "screen" :href stylesheet-url :type "text/css"}]]
+       [:body
+        [:h1 title]
+        [:p (join " " (remove nil? [(get-message :generated-on)
+                                    (java.time.LocalDateTime/now)
+                                    (get-message :by)
+                                    version]))]
+        (if-not
+         (empty? faults)
+          (apply
+           vector
+           :table
+           (html-header-row cols)
+           (map
+            #(html-fault-row % cols)
+            faults))
+          [:p (get-message :no-faults-found)])]]))))
+
+(defn output
+  [content options]
+  (let [faults (filter-severity content (:severity options))]
+    (spit (:output options)
+          (case (:format options)
+            :html (output-html faults options)
+            :csv (output-csv faults)
+            (with-out-str (pprint faults))))))
+
+(defn -main [& args]
+  (let [opts (parse-opts args cli-options)
+        options (assoc (:options opts)
+                       :input (if (= (:input (:options opts)) "standard input")
+                                *in*
+                                (:input (:options opts)))
+                       :output (if (= (:output (:options opts)) "standard output")
+                                 *out*
+                                 (:output (:options opts))))]
+    ;;(println options)
+    (when (:help options)
+      (println (:summary opts)))
+    (when (:errors opts)
+      (println (:errors opts)))
+    (when-not (or (:help options) (:errors options))
+      (binding [*config* (assoc *config* :default-language (:language options))]
+        (output
+         (validate (:input options))
+         options)))))
\ No newline at end of file
diff --git a/src/dog_and_duck/quack/picky/constants.clj b/src/dog_and_duck/quack/picky/constants.clj
index 149cef1..48628d9 100644
--- a/src/dog_and_duck/quack/picky/constants.clj
+++ b/src/dog_and_duck/quack/picky/constants.clj
@@ -90,7 +90,7 @@
   "The set of object types we will accept as nouns.
    
    There's an [explicit set of allowed 'object types']
-   (https://www.w3.org/TR/activitystreams-vocabulary/#activity-types), but by 
+   (https://www.w3.org/TR/activitystreams-vocabulary/#object-types), but by 
    implication it is not exhaustive."
   #{"Article" 
     "Audio" 
diff --git a/src/dog_and_duck/scratch/core.clj b/src/dog_and_duck/quack/picky/distribution.clj
similarity index 61%
rename from src/dog_and_duck/scratch/core.clj
rename to src/dog_and_duck/quack/picky/distribution.clj
index 2b1975b..bdcb91f 100644
--- a/src/dog_and_duck/scratch/core.clj
+++ b/src/dog_and_duck/quack/picky/distribution.clj
@@ -1,4 +1,4 @@
-(ns dog-and-duck.scratch.core)
+(ns dog-and-duck.quack.picky.distribution)
 
 ;;;     Copyright (C) Simon Brooke, 2022
 
@@ -16,7 +16,15 @@
 ;;;     along with this program; if not, write to the Free Software
 ;;;     Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 
-(defn foo
-  "I don't do a whole lot."
-  [x]
-  (println x "Hello, World!"))
+(defn distribution
+  "Distribution of values of function `f` when applied to `vals`.
+   
+   I *know* there's a library function that does this, probably better, but I
+   don't remember what it's called!"
+  [f vals]
+  (loop [result {} values vals]
+    (if (empty? values) result 
+        (let [r (apply f (list (first values)))]
+                  (recur 
+                   (assoc result r (if (result r) (inc (result r)) 1)) 
+                   (rest values))))))
\ No newline at end of file
diff --git a/src/dog_and_duck/quack/picky/objects.clj b/src/dog_and_duck/quack/picky/objects.clj
index 9d4b730..0668100 100644
--- a/src/dog_and_duck/quack/picky/objects.clj
+++ b/src/dog_and_duck/quack/picky/objects.clj
@@ -365,7 +365,7 @@
 
 (defn check-property-valid
   [obj prop clause]
-  (info "obj" obj "prop" prop "clause" clause)
+  ;; (info "obj" obj "prop" prop "clause" clause)
   (let [val (obj prop)
         validator (:validator clause)
         [severity token] (:if-invalid clause)]
diff --git a/src/dog_and_duck/quack/picky/scratch.clj b/src/dog_and_duck/quack/picky/scratch.clj
index 690417e..505e030 100644
--- a/src/dog_and_duck/quack/picky/scratch.clj
+++ b/src/dog_and_duck/quack/picky/scratch.clj
@@ -3,62 +3,51 @@
   (:require [clojure.data.json :refer [read-str]]
             [clojure.java.io :refer [file]]
             [clojure.walk :refer [keywordize-keys]]
+            [dog-and-duck.quack.picky.distribution :refer [distribution]]
             [dog-and-duck.quack.picky.objects :refer
              [object-faults properties-faults]]
             [dog-and-duck.quack.picky.utils :refer [concat-non-empty
                                                     filter-severity]]))
 
-(def files (filter
-            #(and (.isFile %) (.endsWith (.getName %) ".json"))
-            (file-seq (file "resources/activitystreams-test-documents"))))
+;; (def files (filter
+;;             #(and (.isFile %) (.endsWith (.getName %) ".json"))
+;;             (file-seq (file "resources/activitystreams-test-documents"))))
 
-(def r
-  (reduce
-   concat-non-empty
-   (map
-    #(try
-       (let [contents (read-str (slurp %))
-             faults (cond (map? contents) (filter-severity
-                                           (object-faults
-                                            (keywordize-keys contents))
-                                           :should)
-                        ;;   (coll? contents) (apply
-                        ;;                     concat-non-empty
-                        ;;                     (map (fn [obj]
-                        ;;                            (object-faults
-                        ;;                             (keywordize-keys obj)))
-                        ;;                          contents))
-                          )]
-         (map (fn [f] (assoc f :document (.getName %))) faults))
-       (catch Exception any
-         [(.getName %) (str "Exception "
-                            (.getName (.getClass any))
-                            ": "
-                            (.getMessage any))]))
-    (filter
-     #(and (.isFile %) (.endsWith (.getName %) ".json"))
-     (file-seq (file "resources/activitystreams-test-documents"))))))
+;; (def r
+;;   (reduce
+;;    concat-non-empty
+;;    (map
+;;     #(try
+;;        (let [contents (read-str (slurp %))
+;;              faults (cond (map? contents) (filter-severity
+;;                                            (object-faults
+;;                                             (keywordize-keys contents))
+;;                                            :should)
+;;                         ;;   (coll? contents) (apply
+;;                         ;;                     concat-non-empty
+;;                         ;;                     (map (fn [obj]
+;;                         ;;                            (object-faults
+;;                         ;;                             (keywordize-keys obj)))
+;;                         ;;                          contents))
+;;                           )]
+;;          (map (fn [f] (assoc f :document (.getName %))) faults))
+;;        (catch Exception any
+;;          [(.getName %) (str "Exception "
+;;                             (.getName (.getClass any))
+;;                             ": "
+;;                             (.getMessage any))]))
+;;     (filter
+;;      #(and (.isFile %) (.endsWith (.getName %) ".json"))
+;;      (file-seq (file "resources/activitystreams-test-documents"))))))
 
-(count (filter-severity (object-faults (keywordize-keys (read-str (slurp "resources/activitystreams-test-documents/vocabulary-ex189-jsonld.json")))) :critical))
+;; (count (filter-severity (object-faults (keywordize-keys (read-str (slurp "resources/activitystreams-test-documents/vocabulary-ex189-jsonld.json")))) :critical))
 
-(count (filter
-        #(and (.isFile %) (.endsWith (.getName %) ".json"))
-        (file-seq (file "resources/activitystreams-test-documents"))))
+;; (count (filter
+;;         #(and (.isFile %) (.endsWith (.getName %) ".json"))
+;;         (file-seq (file "resources/activitystreams-test-documents"))))
 
 ;; (count r)
 ;; (last r)
 ;; (clojure.pprint/pprint (last r))
 
-(defn distribution
-  "Distribution of values of function `f` when applied to `vals`.
-   
-   I *know* there's a library function that does this, probably better, but I
-   don't remember what it's called!"
-  [f vals]
-  (loop [result {} values vals]
-    (cond (empty? values) result
-          :else (let [r (apply f (list (first values)))
-                      i (if (result r) (inc (result r)) 1)]
-                  (recur (assoc result r i) (rest values))))))
-
-(distribution :fault r)
\ No newline at end of file
+;; (distribution :fault r)
\ No newline at end of file
diff --git a/src/dog_and_duck/quack/picky/utils.clj b/src/dog_and_duck/quack/picky/utils.clj
index 3d0342b..9d5eb0f 100644
--- a/src/dog_and_duck/quack/picky/utils.clj
+++ b/src/dog_and_duck/quack/picky/utils.clj
@@ -115,13 +115,20 @@
   "Return a list of reports taken from these `reports` where the severity
    of the report is greater than this or equal to this `severity`."
   [reports severity]
-  (cond (nil? reports) nil
+  (cond (nil? (severity-filters severity)) (throw
+                                             (ex-info
+                                              "Argument `severity` was not a valid severity key"
+                                              {:arguments {:reports reports
+                                                           :severity severity}}))
+    (empty? reports) nil
         (and
          (coll? reports)
          (every? map? reports)
-         (every? :severity reports)) (remove
-                                      #((severity-filters severity) (:severity %))
-                                      reports)
+         (every? :severity reports))(remove
+                                     #(if  (:severity %)
+                                        ((severity-filters severity) (:severity %))
+                                        false)
+                                     reports)
         :else
         (throw
          (ex-info
diff --git a/src/dog_and_duck/scratch/scratch.clj b/src/dog_and_duck/scratch/scratch.clj
index 305bceb..54aee05 100644
--- a/src/dog_and_duck/scratch/scratch.clj
+++ b/src/dog_and_duck/scratch/scratch.clj
@@ -34,15 +34,15 @@
 ;;; Retrieve the account details from its home server
 ;;; (`keywordize-keys` is not necessary here but produces a more idiomatic clojure
 ;;; data structure)
-(def account
-  (-> account-handle
-      (webfinger/parse-handle)
-      (webfinger/fetch-user-id!)
-      (activitypub-net/fetch-user!)
-      (select-keys [:name :preferredUsername :inbox :summary])))
+;; (def account
+;;   (-> account-handle
+;;       (webfinger/parse-handle)
+;;       (webfinger/fetch-user-id!)
+;;       (activitypub-net/fetch-user!)
+;;       (select-keys [:name :preferredUsername :inbox :summary])))
 
 ;; ;;; examine what you got back!
-(:inbox account)
+;; (:inbox account)
 
 ;; (-> account
 ;;     :inbox