Feature: Add support for passing headers with HTTP Transport

README.md

@@ -136,6 +136,9 @@ For MCP servers that communicate over HTTP:
     'api_key' => env('RELAY_GITHUB_SERVER_API_KEY'),
     'timeout' => 30,
     'transport' => Transport::Http,
+    'headers' => [
+        'User-Agent' => 'prism-php-relay/1.0',
+    ]
 ],
 ```
 

src/Relay.php

@@ -340,7 +340,7 @@ protected function getSchemeParameters(array $properties, string $definitionName
      *
      * @throws RelayException
      */
-    protected function getSchemeParameter(string $name, array $property, string $definitionName): Schema|null
+    protected function getSchemeParameter(string $name, array $property, string $definitionName): ?Schema
     {
         if ($property === []) {
             return null;

src/Transport/HttpTransport.php

@@ -78,6 +78,10 @@ protected function sendHttpRequest(array $payload): Response
                 $this->hasApiKey(),
                 fn ($http) => $http->withToken($this->getApiKey())
             )
+            ->when(
+                $this->hasHeaders(),
+                fn ($http) => $http->withHeaders($this->getHeaders())
+            )
             ->post($this->getServerUrl(), $payload);
     }
 
@@ -91,11 +95,26 @@ protected function hasApiKey(): bool
         return isset($this->config['api_key']) && $this->config['api_key'] !== null;
     }
 
+    protected function hasHeaders(): bool
+    {
+        return isset($this->config['headers'])
+            && is_array($this->config['headers'])
+            && ! empty($this->config['headers']);
+    }
+
     protected function getApiKey(): string
     {
         return (string) ($this->config['api_key'] ?? '');
     }
 
+    /**
+     * @return array<string, mixed>
+     */
+    protected function getHeaders(): array
+    {
+        return $this->config['headers'] ?? [];
+    }
+
     protected function getServerUrl(): string
     {
         return $this->config['url'];

tests/Unit/Transport/HttpTransportTest.php

@@ -202,3 +202,25 @@
 
     Http::assertSent(fn ($request) => $request->hasHeader('Accept', 'application/json'));
 });
+
+it('supports passing arbitrary request headers', function (): void {
+    $transport = new HttpTransport([
+        'url' => 'http://example.com/api',
+        'timeout' => 30,
+        'headers' => [
+            'User-Agent' => 'prism-php-relay/1.0',
+        ],
+    ]);
+
+    Http::fake([
+        'http://example.com/api' => Http::response([
+            'jsonrpc' => '2.0',
+            'id' => '1',
+            'result' => ['status' => 'success'],
+        ]),
+    ]);
+
+    $transport->sendRequest('test/method');
+
+    Http::assertSent(fn ($request) => $request->hasHeader('User-Agent', 'prism-php-relay/1.0'));
+});