diff --git a/scripts/get_ws_changes.php b/scripts/get_ws_changes.php
new file mode 100644
index 000000000..d5b91f9f0
--- /dev/null
+++ b/scripts/get_ws_changes.php
@@ -0,0 +1,99 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Script for converting a PHP WS structure to a TS type.
+ *
+ * The first parameter (required) is the path to the Moodle installation to use.
+ * The second parameter (required) is the name to the WS to convert.
+ * The third parameter (optional) is a number: 1 to convert the params structure,
+ * 0 to convert the returns structure. Defaults to 0.
+ */
+
+if (!isset($argv[1])) {
+    echo "ERROR: Please pass the path to the folder containing the Moodle installations as the first parameter.\n";
+    die();
+}
+
+
+if (!isset($argv[2])) {
+    echo "ERROR: Please pass the WS name as the second parameter.\n";
+    die();
+}
+
+define('CLI_SCRIPT', true);
+require_once('ws_to_ts_functions.php');
+
+$versions = array('master', '37', '36', '35', '34', '33', '32', '31');
+
+$moodlespath = $argv[1];
+$wsname = $argv[2];
+$useparams = !!(isset($argv[3]) && $argv[3]);
+$pathseparator = '/';
+
+// Get the path to the script.
+$index = strrpos(__FILE__, $pathseparator);
+if ($index === false) {
+    $pathseparator = '\\';
+    $index = strrpos(__FILE__, $pathseparator);
+}
+$scriptfolder = substr(__FILE__, 0, $index);
+$scriptpath = concatenate_paths($scriptfolder, 'get_ws_structure.php', $pathseparator);
+
+$previousstructure = null;
+$previousversion = null;
+$libsloaded = false;
+
+foreach ($versions as $version) {
+    $moodlepath = concatenate_paths($moodlespath, 'stable_' . $version, $pathseparator);
+
+    if (!$libsloaded) {
+        $libsloaded = true;
+
+        require($moodlepath . '/config.php');
+        require($CFG->dirroot . '/webservice/lib.php');
+    }
+
+    // Get the structure in this Moodle version.
+    $structure = shell_exec("php $scriptpath $moodlepath $wsname " . ($useparams ? 'true' : ''));
+
+    if (strpos($structure, 'ERROR:') === 0) {
+        echo "WS not found in version $version. Stop.\n";
+        break;
+    }
+
+    $structure = unserialize($structure);
+
+    if ($previousstructure != null) {
+        echo "*** Check changes from version $version to $previousversion ***\n";
+
+        $messages = detect_ws_changes($previousstructure, $structure);
+
+        if (count($messages) > 0) {
+            $haschanged = true;
+
+            foreach($messages as $message) {
+                echo "$message\n";
+            }
+        } else {
+            echo "No changes found.\n";
+        }
+        echo "\n";
+    }
+
+    $previousstructure = $structure;
+    $previousversion = $version;
+}
diff --git a/scripts/get_ws_structure.php b/scripts/get_ws_structure.php
new file mode 100644
index 000000000..bfa975ee9
--- /dev/null
+++ b/scripts/get_ws_structure.php
@@ -0,0 +1,55 @@
+<?php
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * Script for getting the PHP structure of a WS returns or params.
+ *
+ * The first parameter (required) is the path to the Moodle installation to use.
+ * The second parameter (required) is the name to the WS to convert.
+ * The third parameter (optional) is a number: 1 to convert the params structure,
+ * 0 to convert the returns structure. Defaults to 0.
+ */
+
+if (!isset($argv[1])) {
+    echo "ERROR: Please pass the Moodle path as the first parameter.\n";
+    die();
+}
+
+
+if (!isset($argv[2])) {
+    echo "ERROR: Please pass the WS name as the second parameter.\n";
+    die();
+}
+
+$moodlepath = $argv[1];
+$wsname = $argv[2];
+$useparams = !!(isset($argv[3]) && $argv[3]);
+
+define('CLI_SCRIPT', true);
+
+require($moodlepath . '/config.php');
+require($CFG->dirroot . '/webservice/lib.php');
+require_once('ws_to_ts_functions.php');
+
+$structure = get_ws_structure($wsname, $useparams);
+
+if ($structure === false) {
+    echo "ERROR: The WS wasn't found in this Moodle installation.\n";
+    die();
+}
+
+remove_default_closures($structure);
+echo serialize($structure);
diff --git a/scripts/get_ws_ts.php b/scripts/get_ws_ts.php
index 4c93260ec..900a153b8 100644
--- a/scripts/get_ws_ts.php
+++ b/scripts/get_ws_ts.php
@@ -20,8 +20,8 @@
  * The first parameter (required) is the path to the Moodle installation to use.
  * The second parameter (required) is the name to the WS to convert.
  * The third parameter (optional) is the name to put to the TS type. Defaults to "TypeName".
- * The fourth parameter (optional) is a boolean: true to convert the params structure,
- * false to convert the returns structure. Defaults to false.
+ * The fourth parameter (optional) is a number: 1 to convert the params structure,
+ * 0 to convert the returns structure. Defaults to 0.
  */
 
 if (!isset($argv[1])) {
@@ -46,23 +46,16 @@ require($moodlepath . '/config.php');
 require($CFG->dirroot . '/webservice/lib.php');
 require_once('ws_to_ts_functions.php');
 
-// get all the function descriptions
-$functions = $DB->get_records('external_functions', array(), 'name');
-$functiondescs = array();
-foreach ($functions as $function) {
-    $functiondescs[$function->name] = external_api::external_function_info($function);
-}
+$structure = get_ws_structure($wsname, $useparams);
 
-if (!isset($functiondescs[$wsname])) {
+if ($structure === false) {
     echo "ERROR: The WS wasn't found in this Moodle installation.\n";
     die();
 }
 
 if ($useparams) {
-    $structure = $functiondescs[$wsname]->parameters_desc;
     $description = "Params of WS $wsname.";
 } else {
-    $structure = $functiondescs[$wsname]->returns_desc;
     $description = "Result of WS $wsname.";
 }
 
diff --git a/scripts/ws_to_ts_functions.php b/scripts/ws_to_ts_functions.php
index c6eb60332..ca05d2082 100644
--- a/scripts/ws_to_ts_functions.php
+++ b/scripts/ws_to_ts_functions.php
@@ -18,6 +18,28 @@
  * Helper functions for converting a Moodle WS structure to a TS type.
  */
 
+/**
+ * Get the structure of a WS params or returns.
+ */
+function get_ws_structure($wsname, $useparams) {
+    global $DB;
+
+    // get all the function descriptions
+    $functions = $DB->get_records('external_functions', array(), 'name');
+    $functiondescs = array();
+    foreach ($functions as $function) {
+        $functiondescs[$function->name] = external_api::external_function_info($function);
+    }
+
+    if (!isset($functiondescs[$wsname])) {
+        return false;
+    } else if ($useparams) {
+        return $functiondescs[$wsname]->parameters_desc;
+    } else {
+        return $functiondescs[$wsname]->returns_desc;
+    }
+}
+
 /**
  * Fix a comment: make sure first letter is uppercase and add a dot at the end if needed.
  */
@@ -136,3 +158,87 @@ function convert_to_ts($key, $value, $boolisnumber = false, $indentation = '', $
         return "";
     }
 }
+
+/**
+ * Concatenate two paths.
+ */
+function concatenate_paths($left, $right, $separator = '/') {
+    if (!is_string($left) || $left == '') {
+        return $right;
+    } else if (!is_string($right) || $right == '') {
+        return $left;
+    }
+
+    $lastCharLeft = substr($left, -1);
+    $firstCharRight = $right[0];
+
+    if ($lastCharLeft === $separator && $firstCharRight === $separator) {
+        return $left . substr($right, 1);
+    } else if ($lastCharLeft !== $separator && $firstCharRight !== '/') {
+        return $left . '/' . $right;
+    } else {
+        return $left . $right;
+    }
+}
+
+/**
+ * Detect changes between 2 WS structures. We only detect fields that have been added or modified, not removed fields.
+ */
+function detect_ws_changes($new, $old, $key = '', $path = '') {
+    $messages = [];
+
+    if (gettype($new) != gettype($old)) {
+        // The type has changed.
+        $messages[] = "Property '$key' has changed type, from '" . gettype($old) . "' to '" . gettype($new) .
+                        ($path != '' ? "' inside $path." : "'.");
+
+    } else if ($new instanceof external_value && $new->type != $old->type) {
+        // The type has changed.
+        $messages[] = "Property '$key' has changed type, from '" . $old->type . "' to '" . $new->type .
+                        ($path != '' ? "' inside $path." : "'.");
+
+    } else if ($new instanceof external_warnings || $new instanceof external_files) {
+        // Ignore these types.
+
+    } else if ($new instanceof external_single_structure) {
+        // Check each subproperty.
+        $newpath = ($path != '' ? "$path." : '') . $key;
+
+        foreach ($new->keys as $subkey => $value) {
+            if (!isset($old->keys[$subkey])) {
+                // New property.
+                $messages[] = "New property '$subkey' found" . ($newpath != '' ? " inside '$newpath'." : '.');
+            } else {
+                $messages = array_merge($messages, detect_ws_changes($value, $old->keys[$subkey], $subkey, $newpath));
+            }
+        }
+    } else if ($new instanceof external_multiple_structure) {
+        // Recursive call with the content.
+        $messages = array_merge($messages, detect_ws_changes($new->content, $old->content, $key, $path));
+    }
+
+    return $messages;
+}
+
+/**
+ * Remove all closures (anonymous functions) in the default values so the object can be serialized.
+ */
+function remove_default_closures($value) {
+    if ($value instanceof external_warnings || $value instanceof external_files) {
+        // Ignore these types.
+
+    } else if ($value instanceof external_value) {
+        if ($value->default instanceof Closure) {
+            $value->default = null;
+        }
+
+    } else if ($value instanceof external_single_structure) {
+
+        foreach ($value->keys as $key => $subvalue) {
+            remove_default_closures($subvalue);
+        }
+
+    } else if ($value instanceof external_multiple_structure) {
+        remove_default_closures($value->content);
+    }
+}