diff --git a/src/Api/Campaigns.php b/src/Api/Campaigns.php
index 0fe1c24..42691b5 100644
--- a/src/Api/Campaigns.php
+++ b/src/Api/Campaigns.php
@@ -26,6 +26,7 @@ namespace SkillDisplay\PHPToolKit\Api;
 use GuzzleHttp\Client;
 use GuzzleHttp\Exception\ClientException;
 use GuzzleHttp\Psr7\Request;
+use InvalidArgumentException;
 use SkillDisplay\PHPToolKit\Configuration\Settings;
 use SkillDisplay\PHPToolKit\Entity\Campaign;
 
@@ -45,6 +46,9 @@ class Campaigns
 
     public function getForUser(): array
     {
+        if (!$this->settings->getApiKey()) {
+            throw new InvalidArgumentException('Missing API key', 1688660942);
+        }
         $url = $this->settings->getAPIUrl() . '/api/v1/campaigns';
         try {
             $result = $this->client->send(new Request(
diff --git a/src/Api/MemberSkills.php b/src/Api/MemberSkills.php
index ec2c7f6..1920c55 100644
--- a/src/Api/MemberSkills.php
+++ b/src/Api/MemberSkills.php
@@ -6,11 +6,9 @@ namespace SkillDisplay\PHPToolKit\Api;
 
 use GuzzleHttp\Client;
 use GuzzleHttp\Exception\ClientException;
-use GuzzleHttp\Exception\GuzzleException;
+use InvalidArgumentException;
 use SkillDisplay\PHPToolKit\Configuration\Settings;
 use GuzzleHttp\Psr7\Request;
-use SkillDisplay\PHPToolKit\Entity\Campaign;
-use SkillDisplay\PHPToolKit\Entity\MemberSkill;
 use SkillDisplay\PHPToolKit\Entity\MemberSkill as Entity;
 
 class MemberSkills
@@ -32,6 +30,9 @@ class MemberSkills
         if ($id <= 0) {
             throw new \Exception('ID of Organisation has to be a positive integer.');
         }
+        if (!$this->settings->getApiKey()) {
+            throw new InvalidArgumentException('Missing API key', 1688660942);
+        }
         $url = $this->settings->getAPIUrl() . '/api/v1/organisation/' . $id . '/listVerifications/json';
         try {
             $result = $this->client->send(new Request(
diff --git a/src/Api/Organisation.php b/src/Api/Organisation.php
index 67e2bc1..bf65fdd 100644
--- a/src/Api/Organisation.php
+++ b/src/Api/Organisation.php
@@ -6,7 +6,7 @@ namespace SkillDisplay\PHPToolKit\Api;
 
 use GuzzleHttp\Client;
 use GuzzleHttp\Exception\ClientException;
-use GuzzleHttp\Exception\GuzzleException;
+use InvalidArgumentException;
 use SkillDisplay\PHPToolKit\Configuration\Settings;
 use GuzzleHttp\Psr7\Request;
 use SkillDisplay\PHPToolKit\Entity\Organisation as Entity;
@@ -30,7 +30,10 @@ class Organisation
         if ($id <= 0) {
             throw new \Exception('ID of Organisation has to be a positive integer.');
         }
-        $url = $this->settings->getAPIUrl() . '/api/v1/organisation/' . $id . '/statistic';
+        if (!$this->settings->getApiKey()) {
+            throw new InvalidArgumentException('Missing API key', 1688660942);
+        }
+        $url = $this->settings->getAPIUrl() . '/api/v1/organisation/' . $id . '/statistics';
         try {
             $result = $this->client->send(new Request(
                 'GET',
diff --git a/src/Api/SkillSetProgress.php b/src/Api/SkillSetProgress.php
index 788cb0a..14375a9 100644
--- a/src/Api/SkillSetProgress.php
+++ b/src/Api/SkillSetProgress.php
@@ -26,6 +26,7 @@ namespace SkillDisplay\PHPToolKit\Api;
 use GuzzleHttp\Client;
 use GuzzleHttp\Exception\ClientException;
 use GuzzleHttp\Psr7\Request;
+use InvalidArgumentException;
 use SkillDisplay\PHPToolKit\Configuration\Settings;
 use SkillDisplay\PHPToolKit\Entity\SkillSetProgress as Entity;
 
@@ -47,7 +48,9 @@ class SkillSetProgress
         if ($id <= 0) {
             throw new \Exception('ID of SkillSet has to be a positive integer.', 1688639724754);
         }
-
+        if (!$this->settings->getApiKey()) {
+            throw new InvalidArgumentException('Missing API key', 1688660942);
+        }
         $url = $this->settings->getAPIUrl() . '/api/v1/skillset/' . $id . '/progress';
         try {
             $result = $this->client->send(new Request(
@@ -60,7 +63,7 @@ class SkillSetProgress
             ));
         } catch (ClientException $e) {
             if ($e->getCode() === 404) {
-                throw new \InvalidArgumentException('Given SkillSet with id "' . $id . '" not available.', 1688639748718);
+                throw new InvalidArgumentException('Given SkillSet with id "' . $id . '" not available.', 1688639748718);
             }
             throw $e;
         }