diff --git a/src/Schema/JsonRpc/Request.php b/src/Schema/JsonRpc/Request.php
index a4d0c0f4..22083c75 100644
--- a/src/Schema/JsonRpc/Request.php
+++ b/src/Schema/JsonRpc/Request.php
@@ -36,7 +36,7 @@ abstract public static function getMethod(): string;
     /**
      * @param RequestData $data
      */
-    public static function fromArray(array $data): self
+    public static function fromArray(array $data): static
     {
         if (($data['jsonrpc'] ?? null) !== MessageInterface::JSONRPC_VERSION) {
             throw new InvalidArgumentException('Invalid or missing "jsonrpc" version for Request.');
@@ -68,7 +68,7 @@ public static function fromArray(array $data): self
     /**
      * @param array<string, mixed>|null $params
      */
-    abstract protected static function fromParams(?array $params): self;
+    abstract protected static function fromParams(?array $params): static;
 
     public function getId(): string|int
     {
@@ -97,7 +97,7 @@ public function jsonSerialize(): array
     }
 
     /**
-     * @return array<string, mixed>|null
+     * @return array<non-empty-string, mixed>|null
      */
     abstract protected function getParams(): ?array;
 }
diff --git a/src/Schema/Request/CallToolRequest.php b/src/Schema/Request/CallToolRequest.php
index 0bc7fcf3..49bcd0d8 100644
--- a/src/Schema/Request/CallToolRequest.php
+++ b/src/Schema/Request/CallToolRequest.php
@@ -19,7 +19,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class CallToolRequest extends Request
+final class CallToolRequest extends Request
 {
     /**
      * @param string               $name      the name of the tool to invoke
@@ -36,7 +36,7 @@ public static function getMethod(): string
         return 'tools/call';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['name']) || !\is_string($params['name'])) {
             throw new InvalidArgumentException('Missing or invalid "name" parameter for tools/call.');
@@ -58,7 +58,10 @@ protected static function fromParams(?array $params): Request
         );
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{name: string, arguments: array<string, mixed>}
+     */
+    protected function getParams(): array
     {
         return [
             'name' => $this->name,
diff --git a/src/Schema/Request/CompletionCompleteRequest.php b/src/Schema/Request/CompletionCompleteRequest.php
index 324b0041..467bb97c 100644
--- a/src/Schema/Request/CompletionCompleteRequest.php
+++ b/src/Schema/Request/CompletionCompleteRequest.php
@@ -21,7 +21,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class CompletionCompleteRequest extends Request
+final class CompletionCompleteRequest extends Request
 {
     /**
      * @param PromptReference|ResourceReference    $ref      the prompt or resource to complete
@@ -38,7 +38,7 @@ public static function getMethod(): string
         return 'completion/complete';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['ref']) || !\is_array($params['ref'])) {
             throw new InvalidArgumentException('Missing or invalid "ref" parameter for completion/complete.');
@@ -57,7 +57,13 @@ protected static function fromParams(?array $params): Request
         return new self($ref, $params['argument']);
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{
+     *     ref: PromptReference|ResourceReference,
+     *     argument: array{ name: string, value: string }
+     * }
+     */
+    protected function getParams(): array
     {
         return [
             'ref' => $this->ref,
diff --git a/src/Schema/Request/CreateSamplingMessageRequest.php b/src/Schema/Request/CreateSamplingMessageRequest.php
index ae9ea39c..f07a632b 100644
--- a/src/Schema/Request/CreateSamplingMessageRequest.php
+++ b/src/Schema/Request/CreateSamplingMessageRequest.php
@@ -23,7 +23,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class CreateSamplingMessageRequest extends Request
+final class CreateSamplingMessageRequest extends Request
 {
     /**
      * @param SamplingMessage[]     $messages       the messages to send to the model
@@ -59,7 +59,7 @@ public static function getMethod(): string
         return 'sampling/createMessage';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['messages']) || !\is_array($params['messages'])) {
             throw new InvalidArgumentException('Missing or invalid "messages" parameter for sampling/createMessage.');
@@ -86,7 +86,19 @@ protected static function fromParams(?array $params): Request
         );
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{
+     *     messages: SamplingMessage[],
+     *     maxTokens: int,
+     *     preferences?: ModelPreferences,
+     *     systemPrompt?: string,
+     *     includeContext?: string,
+     *     temperature?: float,
+     *     stopSequences?: string[],
+     *     metadata?: array<string, mixed>
+     * }
+     */
+    protected function getParams(): array
     {
         $params = [
             'messages' => $this->messages,
diff --git a/src/Schema/Request/GetPromptRequest.php b/src/Schema/Request/GetPromptRequest.php
index 68954e9c..bc6903f3 100644
--- a/src/Schema/Request/GetPromptRequest.php
+++ b/src/Schema/Request/GetPromptRequest.php
@@ -19,7 +19,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class GetPromptRequest extends Request
+final class GetPromptRequest extends Request
 {
     /**
      * @param string                    $name      the name of the prompt to get
@@ -36,7 +36,7 @@ public static function getMethod(): string
         return 'prompts/get';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['name']) || !\is_string($params['name']) || empty($params['name'])) {
             throw new InvalidArgumentException('Missing or invalid "name" parameter for prompts/get.');
@@ -55,7 +55,10 @@ protected static function fromParams(?array $params): Request
         return new self($params['name'], $arguments);
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{name: string, arguments?: array<string, mixed>}
+     */
+    protected function getParams(): array
     {
         $params = ['name' => $this->name];
 
diff --git a/src/Schema/Request/InitializeRequest.php b/src/Schema/Request/InitializeRequest.php
index 702aa7b3..04db317c 100644
--- a/src/Schema/Request/InitializeRequest.php
+++ b/src/Schema/Request/InitializeRequest.php
@@ -21,7 +21,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class InitializeRequest extends Request
+final class InitializeRequest extends Request
 {
     /**
      * @param string             $protocolVersion The latest version of the Model Context Protocol that the client supports. The client MAY decide to support older versions as well.
@@ -40,7 +40,7 @@ public static function getMethod(): string
         return 'initialize';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['protocolVersion'])) {
             throw new InvalidArgumentException('protocolVersion is required');
@@ -59,7 +59,10 @@ protected static function fromParams(?array $params): Request
         return new self($params['protocolVersion'], $capabilities, $clientInfo);
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{protocolVersion: string, capabilities: ClientCapabilities, clientInfo: Implementation}
+     */
+    protected function getParams(): array
     {
         return [
             'protocolVersion' => $this->protocolVersion,
diff --git a/src/Schema/Request/ListPromptsRequest.php b/src/Schema/Request/ListPromptsRequest.php
index 5f388d66..8c627999 100644
--- a/src/Schema/Request/ListPromptsRequest.php
+++ b/src/Schema/Request/ListPromptsRequest.php
@@ -18,7 +18,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ListPromptsRequest extends Request
+final class ListPromptsRequest extends Request
 {
     /**
      * If provided, the server should return results starting after this cursor.
@@ -35,11 +35,14 @@ public static function getMethod(): string
         return 'prompts/list';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         return new self($params['cursor'] ?? null);
     }
 
+    /**
+     * @return array{cursor:string}|null
+     */
     protected function getParams(): ?array
     {
         $params = [];
diff --git a/src/Schema/Request/ListResourceTemplatesRequest.php b/src/Schema/Request/ListResourceTemplatesRequest.php
index bf6da924..4ce4dfd9 100644
--- a/src/Schema/Request/ListResourceTemplatesRequest.php
+++ b/src/Schema/Request/ListResourceTemplatesRequest.php
@@ -18,7 +18,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ListResourceTemplatesRequest extends Request
+final class ListResourceTemplatesRequest extends Request
 {
     /**
      * @param string|null $cursor An opaque token representing the current pagination position.
@@ -35,11 +35,14 @@ public static function getMethod(): string
         return 'resources/templates/list';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         return new self($params['cursor'] ?? null);
     }
 
+    /**
+     * @return array{cursor:string}|null
+     */
     protected function getParams(): ?array
     {
         $params = [];
diff --git a/src/Schema/Request/ListResourcesRequest.php b/src/Schema/Request/ListResourcesRequest.php
index 85527dff..30c00418 100644
--- a/src/Schema/Request/ListResourcesRequest.php
+++ b/src/Schema/Request/ListResourcesRequest.php
@@ -18,7 +18,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ListResourcesRequest extends Request
+final class ListResourcesRequest extends Request
 {
     /**
      * @param string|null $cursor An opaque token representing the current pagination position.
@@ -35,11 +35,14 @@ public static function getMethod(): string
         return 'resources/list';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         return new self($params['cursor'] ?? null);
     }
 
+    /**
+     * @return array{cursor:string}|null
+     */
     protected function getParams(): ?array
     {
         $params = [];
diff --git a/src/Schema/Request/ListRootsRequest.php b/src/Schema/Request/ListRootsRequest.php
index 3e8fd9fe..35c8a009 100644
--- a/src/Schema/Request/ListRootsRequest.php
+++ b/src/Schema/Request/ListRootsRequest.php
@@ -24,7 +24,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ListRootsRequest extends Request
+final class ListRootsRequest extends Request
 {
     public function __construct(
     ) {
@@ -35,7 +35,7 @@ public static function getMethod(): string
         return 'roots/list';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         return new self();
     }
diff --git a/src/Schema/Request/ListToolsRequest.php b/src/Schema/Request/ListToolsRequest.php
index 56ed591a..00af2863 100644
--- a/src/Schema/Request/ListToolsRequest.php
+++ b/src/Schema/Request/ListToolsRequest.php
@@ -18,7 +18,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ListToolsRequest extends Request
+final class ListToolsRequest extends Request
 {
     /**
      * @param string|null $cursor An opaque token representing the current pagination position.
@@ -35,11 +35,14 @@ public static function getMethod(): string
         return 'tools/list';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         return new self($params['cursor'] ?? null);
     }
 
+    /**
+     * @return array{cursor:string}|null
+     */
     protected function getParams(): ?array
     {
         $params = [];
diff --git a/src/Schema/Request/PingRequest.php b/src/Schema/Request/PingRequest.php
index 13e13202..31fe64bb 100644
--- a/src/Schema/Request/PingRequest.php
+++ b/src/Schema/Request/PingRequest.php
@@ -19,14 +19,14 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class PingRequest extends Request
+final class PingRequest extends Request
 {
     public static function getMethod(): string
     {
         return 'ping';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         return new self();
     }
diff --git a/src/Schema/Request/ReadResourceRequest.php b/src/Schema/Request/ReadResourceRequest.php
index 4aadbe8d..69523eff 100644
--- a/src/Schema/Request/ReadResourceRequest.php
+++ b/src/Schema/Request/ReadResourceRequest.php
@@ -19,10 +19,10 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ReadResourceRequest extends Request
+final class ReadResourceRequest extends Request
 {
     /**
-     * @param string $uri the URI of the resource to read
+     * @param non-empty-string $uri the URI of the resource to read
      */
     public function __construct(
         public readonly string $uri,
@@ -34,7 +34,7 @@ public static function getMethod(): string
         return 'resources/read';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['uri']) || !\is_string($params['uri']) || empty($params['uri'])) {
             throw new InvalidArgumentException('Missing or invalid "uri" parameter for resources/read.');
@@ -43,7 +43,10 @@ protected static function fromParams(?array $params): Request
         return new self($params['uri']);
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{uri: non-empty-string}
+     */
+    protected function getParams(): array
     {
         return [
             'uri' => $this->uri,
diff --git a/src/Schema/Request/ResourceSubscribeRequest.php b/src/Schema/Request/ResourceSubscribeRequest.php
index 0b17b6c1..036785a2 100644
--- a/src/Schema/Request/ResourceSubscribeRequest.php
+++ b/src/Schema/Request/ResourceSubscribeRequest.php
@@ -20,10 +20,10 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ResourceSubscribeRequest extends Request
+final class ResourceSubscribeRequest extends Request
 {
     /**
-     * @param string $uri the URI of the resource to subscribe to
+     * @param non-empty-string $uri the URI of the resource to subscribe to
      */
     public function __construct(
         public readonly string $uri,
@@ -35,7 +35,7 @@ public static function getMethod(): string
         return 'resources/subscribe';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['uri']) || !\is_string($params['uri']) || empty($params['uri'])) {
             throw new InvalidArgumentException('Missing or invalid "uri" parameter for resources/subscribe.');
@@ -44,7 +44,10 @@ protected static function fromParams(?array $params): Request
         return new self($params['uri']);
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{uri: non-empty-string}
+     */
+    protected function getParams(): array
     {
         return ['uri' => $this->uri];
     }
diff --git a/src/Schema/Request/ResourceUnsubscribeRequest.php b/src/Schema/Request/ResourceUnsubscribeRequest.php
index 54349ae8..fd93727b 100644
--- a/src/Schema/Request/ResourceUnsubscribeRequest.php
+++ b/src/Schema/Request/ResourceUnsubscribeRequest.php
@@ -20,10 +20,10 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class ResourceUnsubscribeRequest extends Request
+final class ResourceUnsubscribeRequest extends Request
 {
     /**
-     * @param string $uri the URI of the resource to unsubscribe from
+     * @param non-empty-string $uri the URI of the resource to unsubscribe from
      */
     public function __construct(
         public readonly string $uri,
@@ -35,7 +35,7 @@ public static function getMethod(): string
         return 'resources/unsubscribe';
     }
 
-    protected static function fromParams(?array $params): Request
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['uri']) || !\is_string($params['uri']) || empty($params['uri'])) {
             throw new InvalidArgumentException('Missing or invalid "uri" parameter for resources/unsubscribe.');
@@ -44,7 +44,10 @@ protected static function fromParams(?array $params): Request
         return new self($params['uri']);
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{uri: non-empty-string}
+     */
+    protected function getParams(): array
     {
         return ['uri' => $this->uri];
     }
diff --git a/src/Schema/Request/SetLogLevelRequest.php b/src/Schema/Request/SetLogLevelRequest.php
index 610c241d..ad7bee68 100644
--- a/src/Schema/Request/SetLogLevelRequest.php
+++ b/src/Schema/Request/SetLogLevelRequest.php
@@ -20,7 +20,7 @@
  *
  * @author Kyrian Obikwelu <koshnawaza@gmail.com>
  */
-class SetLogLevelRequest extends Request
+final class SetLogLevelRequest extends Request
 {
     /**
      * @param LoggingLevel $level The level of logging that the client wants to receive from the server. The server
@@ -37,7 +37,7 @@ public static function getMethod(): string
         return 'logging/setLevel';
     }
 
-    protected static function fromParams(?array $params): self
+    protected static function fromParams(?array $params): static
     {
         if (!isset($params['level']) || !\is_string($params['level']) || empty($params['level'])) {
             throw new InvalidArgumentException('Missing or invalid "level" parameter for "logging/setLevel".');
@@ -46,7 +46,10 @@ protected static function fromParams(?array $params): self
         return new self(LoggingLevel::from($params['level']));
     }
 
-    protected function getParams(): ?array
+    /**
+     * @return array{level: value-of<LoggingLevel>}
+     */
+    protected function getParams(): array
     {
         return [
             'level' => $this->level->value,
diff --git a/tests/Schema/JsonRpc/RequestTest.php b/tests/Schema/JsonRpc/RequestTest.php
index a22b9272..279d0953 100644
--- a/tests/Schema/JsonRpc/RequestTest.php
+++ b/tests/Schema/JsonRpc/RequestTest.php
@@ -24,7 +24,7 @@ public static function getMethod(): string
                 return 'foo/bar';
             }
 
-            public static function fromParams(?array $params): self
+            public static function fromParams(?array $params): static
             {
                 return new self();
             }