diff --git a/packages/jsonrpc/src/ensure.ts b/packages/jsonrpc/src/ensure.ts
new file mode 100644
index 0000000..4487637
--- /dev/null
+++ b/packages/jsonrpc/src/ensure.ts
@@ -0,0 +1,31 @@
+import 'reflect-metadata'
+
+export const ensureKey = Symbol('ensure')
+
+export type Validate<Context> = (context: Context) => boolean
+
+export function ensure<Context>(
+  validate: Validate<Context>,
+  message: string = 'Validation failed',
+) {
+  return (
+    target: any,
+    propertyKey: string,
+    // tslint:disable-next-line
+    descriptor: PropertyDescriptor,
+  ) => {
+    const validators: Array<Validate<Context>> =
+      getValidatorsForMethod<Context>(target, propertyKey)
+
+    validators.push(validate)
+
+    Reflect.defineMetadata(ensureKey, validators, target, propertyKey)
+  }
+}
+
+export function getValidatorsForMethod<Context>(
+  target: any,
+  method: string,
+): Array<Validate<Context>> {
+  return Reflect.getOwnMetadata(ensureKey, target, method) || []
+}
diff --git a/packages/jsonrpc/src/express.test.ts b/packages/jsonrpc/src/express.test.ts
index 2e09a38..951a647 100644
--- a/packages/jsonrpc/src/express.test.ts
+++ b/packages/jsonrpc/src/express.test.ts
@@ -4,6 +4,7 @@ import request from 'supertest'
 import {createClient} from './supertest'
 import {jsonrpc} from './express'
 import {noopLogger} from './test-utils'
+import {ensure} from './ensure'
 
 describe('jsonrpc', () => {
 
@@ -22,6 +23,8 @@ describe('jsonrpc', () => {
     addWithContext2(a: number, b: number): Promise<number>
   }
 
+  const ensureLoggedIn = ensure<IContext>(c => !!c.userId)
+
   class Service implements IService {
     constructor(readonly time: number) {}
     add(a: number, b: number) {
@@ -52,16 +55,20 @@ describe('jsonrpc', () => {
     addWithContext = (a: number, b: number) => (ctx: IContext): number => {
       return a + b + ctx.userId
     }
+
+    @ensureLoggedIn
     addWithContext2(a: number, b: number, ctx?: IContext) {
       return Promise.resolve(a + b + ctx!.userId)
     }
   }
 
+  let userId: number | undefined = 1000
   function createApp() {
+    userId = 1000
     const app = express()
     app.use(bodyParser.json())
     app.use('/',
-      jsonrpc(req => ({userId: 1000}), noopLogger)
+      jsonrpc(req => ({userId}), noopLogger)
       .addService('/myService', new Service(5), [
         'add',
         'delay',
@@ -78,7 +85,7 @@ describe('jsonrpc', () => {
 
   const client = createClient<IService>(createApp(), '/myService')
 
-  async function getError(promise: Promise<void>) {
+  async function getError(promise: Promise<unknown>) {
     let error
     try {
       await promise
@@ -153,6 +160,11 @@ describe('jsonrpc', () => {
       const response = await client.addWithContext2(5, 7)
       expect(response).toEqual(1000 + 5 + 7)
     })
+    it('can validate context using @ensure decorator', async () => {
+      userId = undefined
+      const err = await getError(client.addWithContext2(5, 7))
+      expect(err.message).toMatch(/Invalid request/)
+    })
     it('handles synchronous notifications', async () => {
       await request(createApp())
       .post('/myService')
diff --git a/packages/jsonrpc/src/express.ts b/packages/jsonrpc/src/express.ts
index 87c3e52..0204d89 100644
--- a/packages/jsonrpc/src/express.ts
+++ b/packages/jsonrpc/src/express.ts
@@ -2,7 +2,7 @@ import express, {ErrorRequestHandler} from 'express'
 import {FunctionPropertyNames} from './types'
 import {IDEMPOTENT_METHOD_REGEX} from './idempotent'
 import {IErrorResponse} from './error'
-import {ILogger} from '@rondo.dev/common'
+import {ILogger} from '@rondo.dev/logger'
 import {ISuccessResponse} from './jsonrpc'
 import {NextFunction, Request, Response, Router} from 'express'
 import {createError, isJSONRPCError, IJSONRPCError, IError} from './error'
diff --git a/packages/jsonrpc/src/jsonrpc.ts b/packages/jsonrpc/src/jsonrpc.ts
index 7f08527..1b99a52 100644
--- a/packages/jsonrpc/src/jsonrpc.ts
+++ b/packages/jsonrpc/src/jsonrpc.ts
@@ -2,6 +2,7 @@ export type TId = number | string
 import {ArgumentTypes, FunctionPropertyNames, RetType} from './types'
 import {isPromise} from './isPromise'
 import {createError, IErrorResponse, IErrorWithData} from './error'
+import {getValidatorsForMethod} from './ensure'
 
 export const ERROR_PARSE = {
   code: -32700,
@@ -73,6 +74,7 @@ export const createRpcService = <T, M extends FunctionPropertyNames<T>>(
   service: T,
   methods: M[],
 ) => {
+  const rpcService = pick(service, methods)
   return {
     async invoke<Context>(
       req: IRequest<M, ArgumentTypes<T[M]>>,
@@ -94,8 +96,6 @@ export const createRpcService = <T, M extends FunctionPropertyNames<T>>(
 
       const isNotification = req.id === null || req.id === undefined
 
-      const rpcService = pick(service, methods)
-
       if (
         !rpcService.hasOwnProperty(method) ||
         typeof rpcService[method] !== 'function'
@@ -107,6 +107,20 @@ export const createRpcService = <T, M extends FunctionPropertyNames<T>>(
         })
       }
 
+      const validators = getValidatorsForMethod<Context>(
+        (service as any).__proto__, method)
+
+      validators.forEach(v => {
+        const success = v(context)
+        if (!success) {
+          throw createError(ERROR_INVALID_REQUEST, {
+            id,
+            data: null,
+            statusCode: 400,
+          })
+        }
+      })
+
       let retValue = (rpcService[method] as any)(...params, context)
 
       if (typeof retValue === 'function') {
diff --git a/packages/jsonrpc/tsconfig.json b/packages/jsonrpc/tsconfig.json
index 94e864b..301eb59 100644
--- a/packages/jsonrpc/tsconfig.json
+++ b/packages/jsonrpc/tsconfig.json
@@ -1,9 +1,11 @@
 {
   "extends": "../tsconfig.common.json",
   "compilerOptions": {
+    "target": "es5",
     "outDir": "lib",
     "rootDir": "src"
   },
   "references": [
+    {"path": "../logger"}
   ]
 }