diff --git a/Classes/Middleware/ZabbixClient.php b/Classes/Middleware/ZabbixClient.php
index 11f4931..c2f85e3 100644
--- a/Classes/Middleware/ZabbixClient.php
+++ b/Classes/Middleware/ZabbixClient.php
@@ -21,7 +21,6 @@
 use Psr\Http\Server\MiddlewareInterface;
 use TYPO3\CMS\Core\TypoScript\AST\Node\RootNode;
 use TYPO3\CMS\Core\TypoScript\FrontendTypoScript;
-use TYPO3\CMS\Core\Utility\DebugUtility;
 use TYPO3\CMS\Core\Utility\GeneralUtility;
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Http\Server\RequestHandlerInterface;
@@ -98,7 +97,7 @@ private function processRequest(ServerRequestInterface $request)
             } catch (InvalidOperationException $ex){
                 return $response->withStatus(404,  $ex->getMessage());
             } catch (\Exception $ex) {
-                return $response->withStatus(500,  substr(strrchr(get_class($ex), "\\"), 1) . ': '. $ex->getMessage());
+                return $response->withStatus(500,  get_class($ex) . ': '. $ex->getMessage());
             }
         }
 
diff --git a/Classes/Operation/CheckPathExists.php b/Classes/Operation/CheckPathExists.php
index a0124fc..584de7d 100644
--- a/Classes/Operation/CheckPathExists.php
+++ b/Classes/Operation/CheckPathExists.php
@@ -27,10 +27,10 @@ class CheckPathExists implements IOperation, SingletonInterface
     /**
      * execute operation (checkPathExists)
      *
-     * @param array $parameter a path 'path' to a file or folder
+     * @param array|null $parameter a path 'path' to a file or folder
      * @return OperationResult 'file' if path is a file, 'directory' if it's a directory and false if it doesn't exist
      */
-    public function execute($parameter = null)
+    public function execute(array $parameter = null): OperationResult
     {
         $path = $this->getPath($parameter['path']);
         list($path) = glob($path);
@@ -61,9 +61,9 @@ public function execute($parameter = null)
      * prepare path, resolve relative path and resolve EXT: path
      *
      * @param string $path absolute or relative path or EXT:foobar/
-     * @return string/bool false if path is invalid, else the absolute path
+     * @return false|string false if path is invalid, else the absolute path
      */
-    protected function getPath($path)
+    protected function getPath($path): false|string
     {
         // getFileAbsFileName can't handle directory path with trailing / correctly
         if (substr($path, -1) === '/') {
diff --git a/Classes/Operation/Extension/PageSpeedInsights/GetDegradedPageUids.php b/Classes/Operation/Extension/PageSpeedInsights/GetDegradedPageUids.php
index e3ff510..5dc640d 100644
--- a/Classes/Operation/Extension/PageSpeedInsights/GetDegradedPageUids.php
+++ b/Classes/Operation/Extension/PageSpeedInsights/GetDegradedPageUids.php
@@ -31,7 +31,7 @@ class GetDegradedPageUids implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult The extension version
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         if (!ExtensionManagementUtility::isLoaded('pagespeedinsights')) {
             return new OperationResult(false, '');
diff --git a/Classes/Operation/GetApplicationContext.php b/Classes/Operation/GetApplicationContext.php
index 7aa3401..3a883d1 100644
--- a/Classes/Operation/GetApplicationContext.php
+++ b/Classes/Operation/GetApplicationContext.php
@@ -21,7 +21,7 @@ class GetApplicationContext implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult the current application context
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         $applicationContext = Environment::getContext();
diff --git a/Classes/Operation/GetDatabaseAnalyzerSummary.php b/Classes/Operation/GetDatabaseAnalyzerSummary.php
index af52c46..a8ff790 100644
--- a/Classes/Operation/GetDatabaseAnalyzerSummary.php
+++ b/Classes/Operation/GetDatabaseAnalyzerSummary.php
@@ -27,7 +27,7 @@ class GetDatabaseAnalyzerSummary implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult the current application context
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         try {
             $values = [];
diff --git a/Classes/Operation/GetDatabaseVersion.php b/Classes/Operation/GetDatabaseVersion.php
index 127e242..a7f9f7d 100644
--- a/Classes/Operation/GetDatabaseVersion.php
+++ b/Classes/Operation/GetDatabaseVersion.php
@@ -25,7 +25,7 @@ class GetDatabaseVersion implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult the current database version
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $db = [];
         foreach (GeneralUtility::makeInstance(ConnectionPool::class)->getConnectionNames() as $connectionName) {
diff --git a/Classes/Operation/GetDiskSpace.php b/Classes/Operation/GetDiskSpace.php
index 30164e8..6f20b09 100644
--- a/Classes/Operation/GetDiskSpace.php
+++ b/Classes/Operation/GetDiskSpace.php
@@ -27,7 +27,7 @@ class GetDiskSpace implements IOperation, SingletonInterface
      * @param array $parameter
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $path = !empty($parameter['path']) ? $parameter['path'] : '/';
 
diff --git a/Classes/Operation/GetExtensionList.php b/Classes/Operation/GetExtensionList.php
index 31f14b9..b9c0eee 100644
--- a/Classes/Operation/GetExtensionList.php
+++ b/Classes/Operation/GetExtensionList.php
@@ -39,7 +39,7 @@ class GetExtensionList implements IOperation, SingletonInterface
      * @param array $parameter Array of extension locations as string (system, global, local)
      * @return OperationResult The extension list
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $locations = explode(',', $parameter['scopes']);
         if (is_array($locations) && count($locations) > 0) {
diff --git a/Classes/Operation/GetExtensionVersion.php b/Classes/Operation/GetExtensionVersion.php
index 6e82b30..a617e0b 100644
--- a/Classes/Operation/GetExtensionVersion.php
+++ b/Classes/Operation/GetExtensionVersion.php
@@ -29,7 +29,7 @@ class GetExtensionVersion implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult The extension version
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         if (!isset($parameter['extensionKey']) || $parameter['extensionKey'] === '') {
             throw new InvalidArgumentException('no extensionKey set');
diff --git a/Classes/Operation/GetFeatureValue.php b/Classes/Operation/GetFeatureValue.php
index d6c838d..e035125 100644
--- a/Classes/Operation/GetFeatureValue.php
+++ b/Classes/Operation/GetFeatureValue.php
@@ -36,7 +36,7 @@ class GetFeatureValue implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         if (!isset($parameter['feature']) || $parameter['feature'] === '') {
             throw new InvalidArgumentException('feature not set');
diff --git a/Classes/Operation/GetFileSpoolValue.php b/Classes/Operation/GetFileSpoolValue.php
index db63e01..eb6e91a 100644
--- a/Classes/Operation/GetFileSpoolValue.php
+++ b/Classes/Operation/GetFileSpoolValue.php
@@ -30,7 +30,7 @@ class GetFileSpoolValue implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $value = $parameter['value'] ?? null;
         $filePath = $GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport_spool_filepath'] ?? $GLOBALS['TYPO3_CONF_VARS']['MAIL']['spool_file_path'] ?? null;
diff --git a/Classes/Operation/GetFilesystemChecksum.php b/Classes/Operation/GetFilesystemChecksum.php
index bddf564..8afc9e7 100644
--- a/Classes/Operation/GetFilesystemChecksum.php
+++ b/Classes/Operation/GetFilesystemChecksum.php
@@ -32,7 +32,7 @@ class GetFilesystemChecksum implements IOperation, SingletonInterface
      * @param array $parameter Path to a file or folder
      * @return OperationResult The checksum of the given folder or file
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $path = $this->getPath($parameter['path']);
         $getSingleChecksums = $this->getPath($parameter['getSingleChecksums']);
diff --git a/Classes/Operation/GetInsecureExtensionList.php b/Classes/Operation/GetInsecureExtensionList.php
index 1de21bb..e5c32cc 100644
--- a/Classes/Operation/GetInsecureExtensionList.php
+++ b/Classes/Operation/GetInsecureExtensionList.php
@@ -30,7 +30,7 @@ class GetInsecureExtensionList implements IOperation, SingletonInterface
      * @param array $parameter Array of extension locations as string (loaded, existing)
      * @return OperationResult The extension list
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $scope = $parameter['scope'] ?? '';
 
diff --git a/Classes/Operation/GetLastExtensionListUpdate.php b/Classes/Operation/GetLastExtensionListUpdate.php
index 6005ea2..2af9b66 100644
--- a/Classes/Operation/GetLastExtensionListUpdate.php
+++ b/Classes/Operation/GetLastExtensionListUpdate.php
@@ -25,7 +25,7 @@
 class GetLastExtensionListUpdate implements IOperation, SingletonInterface
 {
 
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $typo3Version = GeneralUtility::makeInstance(Typo3Version::class);
         if (!ExtensionManagementUtility::isLoaded('scheduler')) {
diff --git a/Classes/Operation/GetLastSchedulerRun.php b/Classes/Operation/GetLastSchedulerRun.php
index 963aa68..f574349 100644
--- a/Classes/Operation/GetLastSchedulerRun.php
+++ b/Classes/Operation/GetLastSchedulerRun.php
@@ -19,7 +19,7 @@
 class GetLastSchedulerRun implements IOperation, SingletonInterface
 {
 
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         /** @var Registry $registry */
         $registry = GeneralUtility::makeInstance(Registry::class);
diff --git a/Classes/Operation/GetLogResults.php b/Classes/Operation/GetLogResults.php
index 267fe99..6785df3 100644
--- a/Classes/Operation/GetLogResults.php
+++ b/Classes/Operation/GetLogResults.php
@@ -50,7 +50,7 @@ class GetLogResults implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         $filter = $parameter['filter'];
diff --git a/Classes/Operation/GetOpCacheStatus.php b/Classes/Operation/GetOpCacheStatus.php
index fe87ac2..b96659e 100644
--- a/Classes/Operation/GetOpCacheStatus.php
+++ b/Classes/Operation/GetOpCacheStatus.php
@@ -24,7 +24,7 @@ class GetOpCacheStatus implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult the current database version
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         /** @var OpcodeCacheService $opCacheService */
diff --git a/Classes/Operation/GetOutdatedExtensionList.php b/Classes/Operation/GetOutdatedExtensionList.php
index 429de05..27a135d 100644
--- a/Classes/Operation/GetOutdatedExtensionList.php
+++ b/Classes/Operation/GetOutdatedExtensionList.php
@@ -29,7 +29,7 @@ class GetOutdatedExtensionList implements IOperation, SingletonInterface
      * @param array $parameter Array of extension locations as string (system, global, local)
      * @return OperationResult The extension list
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $scope = $parameter['scope'] ?? '';
 
diff --git a/Classes/Operation/GetPHPVersion.php b/Classes/Operation/GetPHPVersion.php
index e06dd47..96053ac 100644
--- a/Classes/Operation/GetPHPVersion.php
+++ b/Classes/Operation/GetPHPVersion.php
@@ -26,7 +26,7 @@ class GetPHPVersion implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult the current PHP version
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         return new OperationResult(true, PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION . '.' . PHP_RELEASE_VERSION);
     }
diff --git a/Classes/Operation/GetProgramVersion.php b/Classes/Operation/GetProgramVersion.php
index d19b3d7..13237b9 100644
--- a/Classes/Operation/GetProgramVersion.php
+++ b/Classes/Operation/GetProgramVersion.php
@@ -27,7 +27,7 @@ class GetProgramVersion implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult the current PHP version
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         if (!isset($parameter['program']) || $parameter['program'] === '') {
diff --git a/Classes/Operation/GetRecord.php b/Classes/Operation/GetRecord.php
index d7ec2fb..c6838d0 100644
--- a/Classes/Operation/GetRecord.php
+++ b/Classes/Operation/GetRecord.php
@@ -46,7 +46,7 @@ class GetRecord implements IOperation, SingletonInterface
      * @param array $parameter A table 'table', field name 'field' and the value 'value' to find the record
      * @return OperationResult The first found record as an array or FALSE if no record was found
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $table = $parameter['table'];
         $field = $parameter['field'];
diff --git a/Classes/Operation/GetRecords.php b/Classes/Operation/GetRecords.php
index 3198729..06e32bf 100644
--- a/Classes/Operation/GetRecords.php
+++ b/Classes/Operation/GetRecords.php
@@ -97,7 +97,7 @@ class GetRecords implements IOperation, SingletonInterface
      * @return OperationResult A set of records as an array or FALSE if no record was found
      * @example ../services/class.FindBlacklistedBePasswordTestService.php This class tests if there are duplicate passwords, besides checking for the presence of blacklisted passwords.
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $table = $parameter['table'];
         $field = $parameter['field'];
diff --git a/Classes/Operation/GetTYPO3Version.php b/Classes/Operation/GetTYPO3Version.php
index af44808..0b1cac1 100644
--- a/Classes/Operation/GetTYPO3Version.php
+++ b/Classes/Operation/GetTYPO3Version.php
@@ -25,7 +25,7 @@ class GetTYPO3Version implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult the current PHP version
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $typo3Version = GeneralUtility::makeInstance(Typo3Version::class);
 
diff --git a/Classes/Operation/GetTotalLogFilesSize.php b/Classes/Operation/GetTotalLogFilesSize.php
index 4ab1442..20b19c4 100644
--- a/Classes/Operation/GetTotalLogFilesSize.php
+++ b/Classes/Operation/GetTotalLogFilesSize.php
@@ -28,7 +28,7 @@ class GetTotalLogFilesSize implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $totalSize = 0;
         $files = GeneralUtility::getFilesInDir(Environment::getVarPath() . '/log/', 'log');
diff --git a/Classes/Operation/GetZabbixLogFileSize.php b/Classes/Operation/GetZabbixLogFileSize.php
index d8f53d0..59bec3c 100644
--- a/Classes/Operation/GetZabbixLogFileSize.php
+++ b/Classes/Operation/GetZabbixLogFileSize.php
@@ -31,7 +31,7 @@ class GetZabbixLogFileSize implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $totalSize = 0;
 
diff --git a/Classes/Operation/HasDeprecationLogEnabled.php b/Classes/Operation/HasDeprecationLogEnabled.php
index 307363c..1e18d79 100644
--- a/Classes/Operation/HasDeprecationLogEnabled.php
+++ b/Classes/Operation/HasDeprecationLogEnabled.php
@@ -36,7 +36,7 @@ class HasDeprecationLogEnabled implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         $errorHandlerErrors = $GLOBALS['TYPO3_CONF_VARS']['SYS']['errorHandlerErrors'];
diff --git a/Classes/Operation/HasExtensionUpdate.php b/Classes/Operation/HasExtensionUpdate.php
index b2da80e..77380ef 100644
--- a/Classes/Operation/HasExtensionUpdate.php
+++ b/Classes/Operation/HasExtensionUpdate.php
@@ -28,7 +28,7 @@ class HasExtensionUpdate implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         if (!isset($parameter['extensionKey']) || $parameter['extensionKey'] === '') {
diff --git a/Classes/Operation/HasFailedSchedulerTask.php b/Classes/Operation/HasFailedSchedulerTask.php
index 7ca8102..53bdbd3 100644
--- a/Classes/Operation/HasFailedSchedulerTask.php
+++ b/Classes/Operation/HasFailedSchedulerTask.php
@@ -29,7 +29,7 @@ class HasFailedSchedulerTask implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         $queryBuilder = GeneralUtility::makeInstance(ConnectionPool::class)->getQueryBuilderForTable('tx_scheduler_task');
         $queryBuilder
diff --git a/Classes/Operation/HasForbiddenUsers.php b/Classes/Operation/HasForbiddenUsers.php
index 0395e3b..791d231 100644
--- a/Classes/Operation/HasForbiddenUsers.php
+++ b/Classes/Operation/HasForbiddenUsers.php
@@ -30,7 +30,7 @@ class HasForbiddenUsers implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         if (!isset($parameter['usernames'])) {
diff --git a/Classes/Operation/HasIPTCPreservation.php b/Classes/Operation/HasIPTCPreservation.php
index 961e299..f65e4e3 100644
--- a/Classes/Operation/HasIPTCPreservation.php
+++ b/Classes/Operation/HasIPTCPreservation.php
@@ -30,7 +30,7 @@ class HasIPTCPreservation implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         return new OperationResult(true, strpos($GLOBALS['TYPO3_CONF_VARS']['GFX']['processor_stripColorProfileCommand'] ?? '','!iptc') !== false);
     }
diff --git a/Classes/Operation/HasMissingDefaultMailSettings.php b/Classes/Operation/HasMissingDefaultMailSettings.php
index 07ea678..7f49df9 100644
--- a/Classes/Operation/HasMissingDefaultMailSettings.php
+++ b/Classes/Operation/HasMissingDefaultMailSettings.php
@@ -28,7 +28,7 @@ class HasMissingDefaultMailSettings implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         if (empty($GLOBALS['TYPO3_CONF_VARS']['MAIL']['defaultMailFromAddress'])) {
diff --git a/Classes/Operation/HasOutdatedVersion.php b/Classes/Operation/HasOutdatedVersion.php
index c8b2074..556467a 100644
--- a/Classes/Operation/HasOutdatedVersion.php
+++ b/Classes/Operation/HasOutdatedVersion.php
@@ -29,7 +29,7 @@ class HasOutdatedVersion implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         /** @var CoreVersionService $coreVersionService */
diff --git a/Classes/Operation/HasRemainingUpdates.php b/Classes/Operation/HasRemainingUpdates.php
index 26cf20e..b839e96 100644
--- a/Classes/Operation/HasRemainingUpdates.php
+++ b/Classes/Operation/HasRemainingUpdates.php
@@ -27,7 +27,7 @@ class HasRemainingUpdates implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         $upgradeWizardsService = GeneralUtility::makeInstance(UpgradeWizardsService::class);
diff --git a/Classes/Operation/HasSecurityUpdate.php b/Classes/Operation/HasSecurityUpdate.php
index 1d6846d..c6318c0 100644
--- a/Classes/Operation/HasSecurityUpdate.php
+++ b/Classes/Operation/HasSecurityUpdate.php
@@ -29,7 +29,7 @@ class HasSecurityUpdate implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         /** @var CoreVersionService $coreVersionService */
         $coreVersionService = GeneralUtility::makeInstance(CoreVersionService::class);
diff --git a/Classes/Operation/HasStrictSyntaxEnabled.php b/Classes/Operation/HasStrictSyntaxEnabled.php
index 7fd70f2..cfb7400 100644
--- a/Classes/Operation/HasStrictSyntaxEnabled.php
+++ b/Classes/Operation/HasStrictSyntaxEnabled.php
@@ -30,7 +30,7 @@ class HasStrictSyntaxEnabled implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
         return new OperationResult(true,
             GeneralUtility::makeInstance(Features::class)->isFeatureEnabled('TypoScript.strictSyntax'));
diff --git a/Classes/Operation/HasUpdate.php b/Classes/Operation/HasUpdate.php
index cd6829a..3bb2c6e 100644
--- a/Classes/Operation/HasUpdate.php
+++ b/Classes/Operation/HasUpdate.php
@@ -29,7 +29,7 @@ class HasUpdate implements IOperation, SingletonInterface
      * @param array $parameter None
      * @return OperationResult
      */
-    public function execute($parameter = [])
+    public function execute(array $parameter = []): OperationResult
     {
 
         /** @var CoreVersionService $coreVersionService */
diff --git a/Classes/Operation/IOperation.php b/Classes/Operation/IOperation.php
index c27b065..4a7d685 100644
--- a/Classes/Operation/IOperation.php
+++ b/Classes/Operation/IOperation.php
@@ -18,5 +18,5 @@ interface IOperation
      * @param array $parameter Parameters for the operation
      * @return OperationResult The operation result
      */
-    public function execute($parameter = []);
+    public function execute(array $parameter = []): OperationResult;
 }