diff --git a/src/UniversalRouter.d.ts b/src/UniversalRouter.d.ts
index 1d7e2dc..1ee52c4 100644
--- a/src/UniversalRouter.d.ts
+++ b/src/UniversalRouter.d.ts
@@ -9,8 +9,8 @@
 
 import pathToRegexp = require('path-to-regexp')
 
-export interface Params {
-  [paramName: string]: any
+export interface QueryParams {
+  [paramName: string]: string | string[]
 }
 
 export interface Context {
@@ -23,33 +23,51 @@ export interface ResolveContext extends Context {
 
 export interface RouteContext<C extends Context, R = any> extends ResolveContext {
   router: UniversalRouter<C, R>
-  route: Route
+  route: Route<C, R>
   baseUrl: string
   path: string
-  params: Params
+  params: QueryParams
   keys: pathToRegexp.Key[]
   next: (resume?: boolean) => Promise<R>
 }
 
+export type Result<T> = T | Promise<T | void> | void
+
 export interface Route<C extends Context = any, R = any> {
   path?: string | RegExp | Array<string | RegExp>
   name?: string
-  parent?: Route | null
+  parent?: Route<C, R> | null
   children?: Routes<C, R> | null
-  action?: (context: RouteContext<C, R> & C, params: Params) => R | Promise<R> | void
+  action?: (context: RouteContext<C, R> & C, params: QueryParams) => Result<R>
 }
 
 export type Routes<C extends Context = Context, R = any> = Array<Route<C, R>>
 
+export type ResolveRoute<C extends Context = Context, R = any> = (
+  context: C & RouteContext<C, R>,
+  params: QueryParams,
+) => Result<R>
+
+export type ErrorHandler<C extends Context = Context, R = any> = (
+  error: Error & { status?: number },
+  context: C & RouteContext<C, R>,
+) => Result<R>
+
 export interface Options<C extends Context = Context, R = any> {
   context?: C
   baseUrl?: string
-  resolveRoute?: (context: C & RouteContext<C, R>, params: Params) => any
-  errorHandler?: (error: Error & { status?: number }, context: C & RouteContext<C, R>) => any
+  resolveRoute?: ResolveRoute<C, R>
+  errorHandler?: ErrorHandler<C, R>
 }
 
 export default class UniversalRouter<C extends Context = Context, R = any> {
   static pathToRegexp: typeof pathToRegexp
-  constructor(routes: Route<C, R> | Routes<C, R>, options?: Options<C>)
+  baseUrl: string
+  errorHandler?: ErrorHandler<C, R>
+  resolveRoute: ResolveRoute<C, R>
+  context: C & { router: UniversalRouter<C, R> }
+  root: Route<C, R>
+  routesByName?: Map<string, Route<C, R>>
+  constructor(routes: Route<C, R> | Routes<C, R>, options?: Options<C, R>)
   resolve(pathnameOrContext: string | ResolveContext): Promise<R>
 }
diff --git a/src/UniversalRouterSync.d.ts b/src/UniversalRouterSync.d.ts
index ae71ab2..0fe6736 100644
--- a/src/UniversalRouterSync.d.ts
+++ b/src/UniversalRouterSync.d.ts
@@ -9,8 +9,8 @@
 
 import pathToRegexp = require('path-to-regexp')
 
-export interface Params {
-  [paramName: string]: any
+export interface QueryParams {
+  [paramName: string]: string | string[]
 }
 
 export interface Context {
@@ -23,33 +23,51 @@ export interface ResolveContext extends Context {
 
 export interface RouteContext<C extends Context, R = any> extends ResolveContext {
   router: UniversalRouter<C, R>
-  route: Route
+  route: Route<C, R>
   baseUrl: string
   path: string
-  params: Params
+  params: QueryParams
   keys: pathToRegexp.Key[]
   next: (resume?: boolean) => R
 }
 
+export type Result<T> = T | void
+
 export interface Route<C extends Context = any, R = any> {
   path?: string | RegExp | Array<string | RegExp>
   name?: string
-  parent?: Route | null
+  parent?: Route<C, R> | null
   children?: Routes<C, R> | null
-  action?: (context: RouteContext<C, R> & C, params: Params) => R | void
+  action?: (context: RouteContext<C, R> & C, params: QueryParams) => Result<R>
 }
 
 export type Routes<C extends Context = Context, R = any> = Array<Route<C, R>>
 
+export type ResolveRoute<C extends Context = Context, R = any> = (
+  context: C & RouteContext<C, R>,
+  params: QueryParams,
+) => Result<R>
+
+export type ErrorHandler<C extends Context = Context, R = any> = (
+  error: Error & { status?: number },
+  context: C & RouteContext<C, R>,
+) => Result<R>
+
 export interface Options<C extends Context = Context, R = any> {
   context?: C
   baseUrl?: string
-  resolveRoute?: (context: C & RouteContext<C, R>, params: Params) => any
-  errorHandler?: (error: Error & { status?: number }, context: C & RouteContext<C, R>) => any
+  resolveRoute?: ResolveRoute<C, R>
+  errorHandler?: ErrorHandler<C, R>
 }
 
 export default class UniversalRouter<C extends Context = Context, R = any> {
   static pathToRegexp: typeof pathToRegexp
-  constructor(routes: Route<C, R> | Routes<C, R>, options?: Options<C>)
+  baseUrl: string
+  errorHandler?: ErrorHandler<C, R>
+  resolveRoute: ResolveRoute<C, R>
+  context: C & { router: UniversalRouter<C, R> }
+  root: Route<C, R>
+  routesByName?: Map<string, Route<C, R>>
+  constructor(routes: Route<C, R> | Routes<C, R>, options?: Options<C, R>)
   resolve(pathnameOrContext: string | ResolveContext): R
 }
diff --git a/src/generateUrls.d.ts b/src/generateUrls.d.ts
index f048c08..e7068b5 100644
--- a/src/generateUrls.d.ts
+++ b/src/generateUrls.d.ts
@@ -8,7 +8,11 @@
  */
 
 import { PathFunctionOptions } from 'path-to-regexp'
-import UniversalRouter, { Params } from './UniversalRouter'
+import UniversalRouter from './UniversalRouter'
+
+export interface Params {
+  [paramName: string]: any
+}
 
 export interface GenerateUrlsOptions extends PathFunctionOptions {
   stringifyQueryParams?: (params: Params) => string
diff --git a/test/generateUrls.test.ts b/test/generateUrls.test.ts
index 53239eb..0834b29 100644
--- a/test/generateUrls.test.ts
+++ b/test/generateUrls.test.ts
@@ -7,8 +7,8 @@
  * LICENSE.txt file in the root directory of this source tree.
  */
 
-import UniversalRouter, { Params } from '../src/UniversalRouter'
-import generateUrls from '../src/generateUrls'
+import UniversalRouter from '../src/UniversalRouter'
+import generateUrls, { Params } from '../src/generateUrls'
 
 const router = new UniversalRouter(
   [