diff --git a/application/Espo/Core/ExternalAccount/ClientManager.php b/application/Espo/Core/ExternalAccount/ClientManager.php
index a9d0c880dc..79bc08b6dd 100644
--- a/application/Espo/Core/ExternalAccount/ClientManager.php
+++ b/application/Espo/Core/ExternalAccount/ClientManager.php
@@ -67,6 +67,10 @@ class ClientManager
      */
     protected $injectableFactory = null;
 
+    /**
+     *
+     * @var array<string,array<string,mixed>>
+     */
     protected $clientMap = [];
 
     public function __construct(
@@ -81,6 +85,14 @@ class ClientManager
         $this->injectableFactory = $injectableFactory;
     }
 
+    /**
+     * @param array{
+     *   accessToken: ?string,
+     *   tokenType: ?string,
+     *   expiresAt?: ?string,
+     *   refreshToken?: ?string,
+     * } $data
+     */
     public function storeAccessToken(string $hash, array $data): void
     {
         if (empty($this->clientMap[$hash]) || empty($this->clientMap[$hash]['externalAccountEntity'])) {
@@ -154,6 +166,7 @@ class ClientManager
             return null;
         }
 
+        /** @var class-string */
         $className = $this->metadata->get("integrations.{$integration}.clientClassName");
 
         $client = $this->injectableFactory->create($className);
@@ -178,6 +191,7 @@ class ClientManager
         /** @var ExternalAccountEntity|null $externalAccountEntity */
         $externalAccountEntity = $this->entityManager->getEntity('ExternalAccount', $integration . '__' . $userId);
 
+        /** @var class-string */
         $className = $this->metadata->get("integrations.{$integration}.clientClassName");
 
         $redirectUri = $this->config->get('siteUrl') . '?entryPoint=oauthCallback';
@@ -245,6 +259,10 @@ class ClientManager
         return $client;
     }
 
+    /**
+     * @param object $client
+     * @return void
+     */
     protected function addToClientMap(
         $client,
         IntegrationEntity $integrationEntity,
@@ -260,6 +278,9 @@ class ClientManager
         ];
     }
 
+    /**
+     * @param object $client
+     */
     protected function getClientRecord($client): Entity
     {
         $data = $this->clientMap[spl_object_hash($client)];
@@ -271,6 +292,9 @@ class ClientManager
         return $data['externalAccountEntity'];
     }
 
+    /**
+     * @param object $client
+     */
     public function isClientLocked($client): bool
     {
         $externalAccountEntity = $this->getClientRecord($client);
diff --git a/application/Espo/Core/ExternalAccount/Clients/IClient.php b/application/Espo/Core/ExternalAccount/Clients/IClient.php
index 5bf17cc77e..31ffdf71b1 100644
--- a/application/Espo/Core/ExternalAccount/Clients/IClient.php
+++ b/application/Espo/Core/ExternalAccount/Clients/IClient.php
@@ -31,12 +31,27 @@ namespace Espo\Core\ExternalAccount\Clients;
 
 interface IClient
 {
+    /**
+     * @param string $name
+     * @return mixed
+     */
     public function getParam($name);
-    
+
+    /**
+     * @param string $name
+     * @param mixed $value
+     * @return mixed
+     */
     public function setParam($name, $value);
-    
+
+    /**
+     * @param array<string,mixed> $params
+     * @return mixed
+     */
     public function setParams(array $params);
 
+    /**
+     * @return bool
+     */
     public function ping();
 }
-
diff --git a/application/Espo/Core/ExternalAccount/Clients/OAuth2Abstract.php b/application/Espo/Core/ExternalAccount/Clients/OAuth2Abstract.php
index 9e29518145..55142f8b2e 100644
--- a/application/Espo/Core/ExternalAccount/Clients/OAuth2Abstract.php
+++ b/application/Espo/Core/ExternalAccount/Clients/OAuth2Abstract.php
@@ -42,12 +42,24 @@ use DateTime;
 
 abstract class OAuth2Abstract implements IClient
 {
+    /**
+     * @var ?Client
+     */
     protected $client = null;
 
+    /**
+     * @var ?ClientManager
+     */
     protected $manager = null;
 
+    /**
+     * @var Log
+     */
     protected $log;
 
+    /**
+     * @var string[]
+     */
     protected $paramList = [
         'endpoint',
         'tokenEndpoint',
@@ -60,16 +72,34 @@ abstract class OAuth2Abstract implements IClient
         'expiresAt',
     ];
 
+    /**
+     * @var ?string
+     */
     protected $clientId = null;
 
+    /**
+     * @var ?string
+     */
     protected $clientSecret = null;
 
+    /**
+     * @var ?string
+     */
     protected $accessToken = null;
 
+    /**
+     * @var ?string
+     */
     protected $refreshToken = null;
 
+    /**
+     * @var ?string
+     */
     protected $redirectUri = null;
 
+    /**
+     * @var ?string
+     */
     protected $expiresAt = null;
 
     const ACCESS_TOKEN_EXPIRATION_MARGIN = '20 seconds';
@@ -78,6 +108,9 @@ abstract class OAuth2Abstract implements IClient
 
     const LOCK_CHECK_STEP = 0.5;
 
+    /**
+     * @param array<string,mixed> $params
+     */
     public function __construct(
         Client $client,
         array $params = [],
@@ -91,6 +124,10 @@ abstract class OAuth2Abstract implements IClient
         $this->setParams($params);
     }
 
+    /**
+     * @param string $name
+     * @return mixed
+     */
     public function getParam($name)
     {
         if (in_array($name, $this->paramList)) {
@@ -100,6 +137,11 @@ abstract class OAuth2Abstract implements IClient
         return null;
     }
 
+    /**
+     * @param string $name
+     * @param mixed $value
+     * @return void
+     */
     public function setParam($name, $value)
     {
         if (in_array($name, $this->paramList)) {
@@ -113,6 +155,10 @@ abstract class OAuth2Abstract implements IClient
         }
     }
 
+    /**
+     * @param array<string,mixed> $params
+     * @return void
+     */
     public function setParams(array $params)
     {
         foreach ($this->paramList as $name) {
@@ -122,6 +168,10 @@ abstract class OAuth2Abstract implements IClient
         }
     }
 
+    /**
+     * @param array<string,mixed> $data
+     * @return void
+     */
     protected function afterTokenRefreshed(array $data): void
     {
         if ($this->manager) {
@@ -129,6 +179,19 @@ abstract class OAuth2Abstract implements IClient
         }
     }
 
+    /**
+     * @param array{
+     *   access_token: string,
+     *   token_type: string,
+     *   refresh_token?: string,
+     *   expires_in?: int,
+     * } $result
+     * @return array{
+     *   accessToken: string,
+     *   tokenType: string,
+     *   expiresAt: ?string,
+     * }
+     */
     protected function getAccessTokenDataFromResponseResult($result): array
     {
         $data = [];
@@ -152,7 +215,12 @@ abstract class OAuth2Abstract implements IClient
     }
 
     /**
-     * @return array|null
+     * @return ?array{
+     *   accessToken: string,
+     *   tokenType: string,
+     *   expiresAt: ?string,
+     *   refreshToken: string,
+     * }
      */
     public function getAccessTokenFromAuthorizationCode(string $code)
     {
@@ -292,7 +360,7 @@ abstract class OAuth2Abstract implements IClient
     /**
      *
      * @param string $url
-     * @param array|string|null $params
+     * @param array<string,mixed>|string|null $params
      * @param string $httpMethod
      * @param ?string $contentType
      * @param bool $allowRenew
@@ -414,6 +482,12 @@ abstract class OAuth2Abstract implements IClient
         return false;
     }
 
+    /**
+     * @param array<string,mixed> $r
+     * @return ?array{
+     *   action: string,
+     * }
+     */
     protected function handleErrorResponse($r)
     {
         if ($r['code'] == 401 && !empty($r['result'])) {
diff --git a/application/Espo/Core/ExternalAccount/OAuth2/Client.php b/application/Espo/Core/ExternalAccount/OAuth2/Client.php
index f05d3bd985..0f9dac2996 100644
--- a/application/Espo/Core/ExternalAccount/OAuth2/Client.php
+++ b/application/Espo/Core/ExternalAccount/OAuth2/Client.php
@@ -58,24 +58,54 @@ class Client
     const GRANT_TYPE_PASSWORD = 'password';
     const GRANT_TYPE_CLIENT_CREDENTIALS = 'client_credentials';
 
+    /**
+     * @var ?string
+     */
     protected $clientId = null;
 
+    /**
+     * @var ?string
+     */
     protected $clientSecret = null;
 
+    /**
+     * @var ?string
+     */
     protected $accessToken = null;
 
+    /**
+     * @var ?string
+     */
     protected $expiresAt = null;
 
+    /**
+     * @var int
+     */
     protected $authType = self::AUTH_TYPE_URI;
 
+    /**
+     * @var string
+     */
     protected $tokenType = self::TOKEN_TYPE_URI;
 
+    /**
+     * @var ?string
+     */
     protected $accessTokenSecret = null;
 
+    /**
+     * @var string
+     */
     protected $accessTokenParamName = 'access_token';
 
+    /**
+     * @var ?string
+     */
     protected $certificateFile = null;
 
+    /**
+     * @var array<string,mixed>
+     */
     protected $curlOptions = [];
 
     public function __construct()
@@ -85,56 +115,110 @@ class Client
         }
     }
 
+    /**
+     * @param string $clientId
+     * @return void
+     */
     public function setClientId($clientId)
     {
         $this->clientId = $clientId;
     }
 
+    /**
+     * @param ?string $clientSecret
+     * @return void
+     */
     public function setClientSecret($clientSecret)
     {
         $this->clientSecret = $clientSecret;
     }
 
+    /**
+     * @param ?string $accessToken
+     * @return void
+     */
     public function setAccessToken($accessToken)
     {
         $this->accessToken = $accessToken;
     }
 
+    /**
+     * @param int $authType
+     * @return void
+     */
     public function setAuthType($authType)
     {
         $this->authType = $authType;
     }
 
+    /**
+     * @param string $certificateFile
+     * @return void
+     */
     public function setCertificateFile($certificateFile)
     {
         $this->certificateFile = $certificateFile;
     }
 
+    /**
+     * @param string $option
+     * @param mixed $value
+     * @return void
+     */
     public function setCurlOption($option, $value)
     {
         $this->curlOptions[$option] = $value;
     }
 
+    /**
+     * @param array<string,mixed> $options
+     * @return void
+     */
     public function setCurlOptions($options)
     {
         $this->curlOptions = array_merge($this->curlOptions, $options);
     }
 
+    /**
+     * @param string $tokenType
+     * @return void
+     */
     public function setTokenType($tokenType)
     {
         $this->tokenType = $tokenType;
     }
 
+    /**
+     * @param ?string $value
+     * @return void
+     */
     public function setExpiresAt($value)
     {
         $this->expiresAt = $value;
     }
 
+    /**
+     * @param ?string $accessTokenSecret
+     * @return void
+     */
     public function setAccessTokenSecret($accessTokenSecret)
     {
         $this->accessTokenSecret = $accessTokenSecret;
     }
 
+    /**
+     * @param string $url
+     * @param array<string,mixed>|string|null $params
+     * @param string $httpMethod
+     * @param array<string,string> $httpHeaders
+     * @return array{
+     *   result: array<string,mixed>|string,
+     *   code: int,
+     *   contentType: string,
+     *   header: string,
+     * }
+     * @throws Exception
+     */
     public function request($url, $params = null, $httpMethod = self::HTTP_METHOD_GET, array $httpHeaders = [])
     {
         if ($this->accessToken) {
@@ -162,6 +246,19 @@ class Client
         return $this->execute($url, $params, $httpMethod, $httpHeaders);
     }
 
+    /**
+     * @param string $url
+     * @param array<string,mixed>|string|null $params
+     * @param string $httpMethod
+     * @param array<string,string> $httpHeaders
+     * @return array{
+     *   result: array<string,mixed>|string,
+     *   code: int,
+     *   contentType: string,
+     *   header: string,
+     * }
+     * @throws Exception
+     */
     private function execute($url, $params, $httpMethod, array $httpHeaders = [])
     {
         $curlOptions = [
@@ -267,6 +364,21 @@ class Client
         ];
     }
 
+    /**
+     * @param string $url
+     * @param string $grantType
+     * @param array{
+     *   client_id?: string,
+     *   client_secret?: string,
+     * } $params
+     * @return array{
+     *   result: array<string,mixed>|string,
+     *   code: int,
+     *   contentType: string,
+     *   header: string,
+     * }
+     * @throws Exception
+     */
     public function getAccessToken($url, $grantType, array $params)
     {
         $params['grant_type'] = $grantType;