diff --git a/src/Model/Filter.php b/src/Model/Filter.php
index dd6686c..76b14ff 100644
--- a/src/Model/Filter.php
+++ b/src/Model/Filter.php
@@ -15,7 +15,7 @@ class Filter
     /**
      * @return static
      */
-    public static function create()
+    public static function create(): self
     {
         return new static();
     }
@@ -25,7 +25,7 @@ class Filter
      *
      * @return $this
      */
-    public function has($value)
+    public function has(string $value): self
     {
         $this->properties['hasTheWord'] = $value;
 
@@ -37,7 +37,7 @@ class Filter
      *
      * @return $this
      */
-    public function hasNot($value)
+    public function hasNot(string $value): self
     {
         $this->properties['doesNotHaveTheWord'] = $value;
 
@@ -49,7 +49,7 @@ class Filter
      *
      * @return $this
      */
-    public function from($values)
+    public function from($values): self
     {
         if (!empty($values)) {
             $this->properties['from'] = collect($values)->map(function ($value) {
@@ -65,7 +65,7 @@ class Filter
      *
      * @return $this
      */
-    public function to($values)
+    public function to($values): self
     {
         if (!empty($values)) {
             $this->properties['to'] = collect($values)->map(function ($value) {
@@ -81,7 +81,7 @@ class Filter
      *
      * @return $this
      */
-    public function subject($values)
+    public function subject($values): self
     {
         $this->properties['subject'] = collect($values)->map(function ($value) {
             return json_encode($value);
@@ -93,7 +93,7 @@ class Filter
     /**
      * @return $this
      */
-    public function hasAttachment()
+    public function hasAttachment(): self
     {
         $this->properties['hasAttachment'] = 'true';
 
@@ -107,7 +107,7 @@ class Filter
      *
      * @return $this
      */
-    public function fromList($value)
+    public function fromList($value): self
     {
         $value = collect($value)->implode(self::SEPARATOR);
         $this->has("list:{$value}");
@@ -118,7 +118,7 @@ class Filter
     /**
      * @return $this
      */
-    public function excludeChats()
+    public function excludeChats(): self
     {
         $this->properties['excludeChats'] = 'true';
 
@@ -130,7 +130,7 @@ class Filter
      *
      * @return $this
      */
-    public function label($label)
+    public function label(string $label): self
     {
         $this->properties['label'] = $label;
 
@@ -140,7 +140,7 @@ class Filter
     /**
      * @return $this
      */
-    public function archive()
+    public function archive(): self
     {
         $this->properties['shouldArchive'] = 'true';
 
@@ -152,7 +152,7 @@ class Filter
      *
      * @return $this
      */
-    public function labelAndArchive($label)
+    public function labelAndArchive(string $label): self
     {
         $this->label($label)->archive();
 
@@ -162,7 +162,7 @@ class Filter
     /**
      * @return $this
      */
-    public function spam()
+    public function spam(): self
     {
         $this->properties['shouldSpam'] = 'true';
         $this->properties['shouldNeverSpam'] = 'false';
@@ -173,7 +173,7 @@ class Filter
     /**
      * @return $this
      */
-    public function neverSpam()
+    public function neverSpam(): self
     {
         $this->properties['shouldSpam'] = 'false';
         $this->properties['shouldNeverSpam'] = 'true';
@@ -184,7 +184,7 @@ class Filter
     /**
      * @return $this
      */
-    public function trash()
+    public function trash(): self
     {
         $this->properties['shouldTrash'] = 'true';
 
@@ -194,7 +194,7 @@ class Filter
     /**
      * @return $this
      */
-    public function read()
+    public function read(): self
     {
         $this->properties['markAsRead'] = 'true';
 
@@ -204,7 +204,7 @@ class Filter
     /**
      * @return $this
      */
-    public function star()
+    public function star(): self
     {
         $this->properties['shouldStar'] = 'true';
 
@@ -216,7 +216,7 @@ class Filter
      *
      * @return $this
      */
-    public function forward($to)
+    public function forward(string $to): self
     {
         $this->properties['forwardTo'] = $to;
 
@@ -226,7 +226,7 @@ class Filter
     /**
      * @return $this
      */
-    public function important()
+    public function important(): self
     {
         $this->properties['shouldAlwaysMarkAsImportant'] = 'true';
 
@@ -236,7 +236,7 @@ class Filter
     /**
      * @return $this
      */
-    public function notImportant()
+    public function notImportant(): self
     {
         $this->properties['shouldNeverMarkAsImportant'] = 'true';
 
@@ -248,7 +248,7 @@ class Filter
      *
      * @return $this
      */
-    public function categorise($category)
+    public function categorise(string $category): self
     {
         $this->properties['smartLabelToApply'] = $category;
 
@@ -261,7 +261,7 @@ class Filter
      * @return array
      * @deprecated toArray()
      */
-    public function getProperties()
+    public function getProperties(): array
     {
         return $this->properties;
     }
@@ -271,7 +271,7 @@ class Filter
      *
      * @return array
      */
-    public function toArray()
+    public function toArray(): array
     {
         return $this->properties;
     }
diff --git a/src/Service/Builder.php b/src/Service/Builder.php
index 509fe37..40bc4c2 100644
--- a/src/Service/Builder.php
+++ b/src/Service/Builder.php
@@ -39,7 +39,7 @@ class Builder
         $this->build();
     }
 
-    public function __toString()
+    public function __toString(): string
     {
         return $this->build();
     }
@@ -49,7 +49,7 @@ class Builder
      *
      * @return string
      */
-    public function getXml()
+    public function getXml(): string
     {
         return $this->xml;
     }
@@ -59,7 +59,7 @@ class Builder
      *
      * @return string
      */
-    private function build()
+    private function build(): void
     {
         $prefix = "<?xml version='1.0' encoding='UTF-8'?>" . PHP_EOL . "<feed xmlns='http://www.w3.org/2005/Atom' xmlns:apps='http://schemas.google.com/apps/2006'>";
         $suffix = '</feed>';
@@ -82,11 +82,13 @@ class Builder
      *
      * @return string
      */
-    private function buildEntry(Filter $filter)
+    private function buildEntry(Filter $filter): string
     {
-        $entry = collect($filter->getProperties())->map(function ($value, $key) {
-            return $this->buildProperty($value, $key);
-        })->implode(PHP_EOL);
+        $entry = collect($filter->toArray())
+            ->map(function ($value, $key): string {
+                return $this->buildProperty($value, $key);
+            })
+            ->implode(PHP_EOL);
 
         return collect(['<entry>', $entry, '</entry>'])->implode(PHP_EOL);
     }
@@ -99,7 +101,7 @@ class Builder
      *
      * @return string
      */
-    private function buildProperty($value, $key)
+    private function buildProperty($value, $key): string
     {
         if (collect(['from', 'to'])->contains($key)) {
             $value = $this->implode($value);
@@ -114,7 +116,7 @@ class Builder
     /**
      * Implode values with the appropriate prefix, suffix and separator.
      */
-    private function implode($value, $separator = '|')
+    private function implode($value, $separator = '|'): string
     {
         if (is_string($value)) {
             return $value;
diff --git a/src/Service/Partials.php b/src/Service/Partials.php
index 70fe0cb..472c092 100644
--- a/src/Service/Partials.php
+++ b/src/Service/Partials.php
@@ -14,7 +14,7 @@ class Partials
      *
      * @return array The loaded filters.
      */
-    public static function load($directoryName = 'filters')
+    public static function load($directoryName = 'filters'): array
     {
         $files = static::getFilePattern($directoryName);
 
@@ -23,7 +23,7 @@ class Partials
                 return include $filename;
             })
             ->flatten(1)
-            ->all();
+            ->toArray();
     }
 
     /**
@@ -36,7 +36,7 @@ class Partials
      *
      * @return string The full path.
      */
-    protected static function getFilePattern($directoryName)
+    protected static function getFilePattern($directoryName): string
     {
         return getcwd() . DIRECTORY_SEPARATOR . $directoryName . DIRECTORY_SEPARATOR . '*.php';
     }
diff --git a/tests/Unit/Service/PartialsTest.php b/tests/Unit/Service/PartialsTest.php
index 802f1bf..d9ab241 100644
--- a/tests/Unit/Service/PartialsTest.php
+++ b/tests/Unit/Service/PartialsTest.php
@@ -18,9 +18,9 @@ class PartialsTest extends TestCase
 
         $this->assertCount(3, $filters);
 
-        $this->assertSame('foo@example.com', $filters[0]->getProperties()['from'][0]);
-        $this->assertSame('bar@example.com', $filters[1]->getProperties()['from'][0]);
-        $this->assertSame('baz@example.com', $filters[2]->getProperties()['from'][0]);
+        $this->assertSame('foo@example.com', $filters[0]->toArray()['from'][0]);
+        $this->assertSame('bar@example.com', $filters[1]->toArray()['from'][0]);
+        $this->assertSame('baz@example.com', $filters[2]->toArray()['from'][0]);
     }
 }
 
@@ -29,7 +29,7 @@ class FakePartials extends Partials
     /**
      * {@inheritdoc}
      */
-    protected static function getFilePattern($directoryName)
+    protected static function getFilePattern($directoryName): string
     {
         return __DIR__ . '/../../stubs/filters/*.php';
     }