diff --git a/extensions/api.d.ts b/extensions/api.d.ts
new file mode 100644
index 000000000..863519e20
--- /dev/null
+++ b/extensions/api.d.ts
@@ -0,0 +1,40 @@
+import type { RequestHandler } from 'express';
+
+declare global {
+  namespace Express {
+    interface Request {
+      actor: any; // TODO
+    }
+  }
+}
+
+type EndpointOptions = {
+  allowedMethods?: string[]
+  subdomain?: string
+  noauth?: boolean
+}
+
+type HttpMethod = 'get' | 'post' | 'put' | 'delete' | 'patch';
+
+type AddRouteFunction = (path: string, options: EndpointOptions, handler: RequestHandler) => void
+
+type RouterMethods = {
+  [K in HttpMethod]: {
+    (path: string, options: EndpointOptions, handler: RequestHandler): void;
+    (path: string, handler: RequestHandler, options?: EndpointOptions): void;
+  };
+}
+
+interface Extension extends RouterMethods {
+  // import(module: 'core'): {
+  //   UserActorType: typeof UserActorType;
+  // };
+  import(module: string): any;
+}
+
+declare global {
+  // Declare the extension variable
+  const extension: Extension;
+}
+
+export {};
diff --git a/extensions/jsconfig.json b/extensions/jsconfig.json
new file mode 100644
index 000000000..0da51fce3
--- /dev/null
+++ b/extensions/jsconfig.json
@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "CommonJS",
+    "moduleResolution": "node",
+    "baseUrl": ".",
+    "paths": {
+      "../src/*": ["../src/*"]
+    },
+    "allowJs": true,
+    "checkJs": true
+  },
+  "include": [
+    "**/*.js",
+    "**/*.d.ts"
+  ]
+}
\ No newline at end of file
diff --git a/extensions/tsconfig.json b/extensions/tsconfig.json
new file mode 100644
index 000000000..187f89a33
--- /dev/null
+++ b/extensions/tsconfig.json
@@ -0,0 +1,20 @@
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "CommonJS",
+    "moduleResolution": "node",
+    "baseUrl": ".",
+    "paths": {
+      "../src/*": ["../src/*"]
+    },
+    "typeRoots": ["../node_modules/@types"],
+    "esModuleInterop": true,
+    "allowSyntheticDefaultImports": true,
+    "strict": true
+  },
+  "include": [
+    "**/*.ts",
+    "**/*.js",
+    "*.d.ts"
+  ]
+}
\ No newline at end of file