diff --git a/src/openapi-lambda-adapters.test.ts b/src/openapi-lambda-adapters.test.ts
index e6af289..c2ff475 100644
--- a/src/openapi-lambda-adapters.test.ts
+++ b/src/openapi-lambda-adapters.test.ts
@@ -1,4 +1,4 @@
-import { APIGatewayProxyStructuredResultV2 } from 'aws-lambda'
+import { APIGatewayProxyStructuredResultV2, Context } from 'aws-lambda'
 import { AxiosRequestConfig } from 'axios'
 import { AxiosError, HttpMethod, Operation } from 'openapi-client-axios'
 import { convertAxiosToApiGw, convertApiGwToAxios } from './openapi-lambda-adapters'
@@ -26,7 +26,8 @@ describe('Adapt axios request/response to AWS Lambda Proxy Event/Response', () =
       // then
       const event = convertAxiosToApiGw(axiosConfig, operation)
       expect(event.rawPath).toEqual('/v1/users')
-      expect(Object.keys(event.headers).length).toEqual(2)
+      expect(Object.keys(event.headers)).toContain('Accept')
+      expect(Object.keys(event.headers)).toContain('authorization')
       expect(event.pathParameters).toEqual({})
       expect(event.queryStringParameters).toEqual({})
       expect(event.rawQueryString).toEqual('')
@@ -204,7 +205,52 @@ describe('Adapt axios request/response to AWS Lambda Proxy Event/Response', () =
       expect(event.headers['x-null']).toBeUndefined()
       expect(event.headers['x-undefined']).toBeUndefined()
     })
-    
+
+    it('defaults to lambda arn the user agent when passed in the context', () => {
+      // given
+      const axiosConfig: AxiosRequestConfig = {
+        method: 'get',
+        url: '/v1/users',
+      }
+      const operation: Operation = {
+        path: '/v1/users',
+        method: HttpMethod.Get,
+        responses: {}
+      }
+
+      // then
+      const event = convertAxiosToApiGw(axiosConfig, operation, {
+        invokedFunctionArn: 'arn:aws:lambda:us-east-1:123456789012:function:my-function'
+      } as Context)
+      
+      expect(event.requestContext.authorizer.lambda)
+      expect(event.requestContext.http.userAgent).toBe('lambda-invoke-arn:aws:lambda:us-east-1:123456789012:function:my-function')
+      expect(event.headers['User-Agent']).toBe('lambda-invoke-arn:aws:lambda:us-east-1:123456789012:function:my-function')
+    })
+
+    it('includes the user agent when passed in the request config', () => {
+      // given
+      const axiosConfig: AxiosRequestConfig = {
+        method: 'get',
+        url: '/v1/users',
+        headers: {
+          'User-Agent': 'daniel-api',
+        }
+      }
+      const operation: Operation = {
+        path: '/v1/users',
+        method: HttpMethod.Get,
+        responses: {}
+      }
+
+      // then
+      const event = convertAxiosToApiGw(axiosConfig, operation, {
+        invokedFunctionArn: 'arn:aws:lambda:us-east-1:123456789012:function:my-function'
+      } as Context)
+      
+      expect(event.requestContext.http.userAgent).toBe('daniel-api')
+      expect(event.headers['User-Agent']).toBe('daniel-api')
+    })
   })
 
   describe('Api GW Proxy Response to Axios Response', () => {
@@ -431,4 +477,4 @@ describe('Adapt axios request/response to AWS Lambda Proxy Event/Response', () =
 
   })
 
-})
\ No newline at end of file
+})
diff --git a/src/openapi-lambda-adapters.ts b/src/openapi-lambda-adapters.ts
index 7620da5..a6a0cde 100644
--- a/src/openapi-lambda-adapters.ts
+++ b/src/openapi-lambda-adapters.ts
@@ -1,6 +1,7 @@
-import {
+import type {
   APIGatewayProxyEventV2, APIGatewayProxyStructuredResultV2,
   APIGatewayProxyEventQueryStringParameters, APIGatewayProxyEventPathParameters,
+  APIGatewayProxyEventV2WithLambdaAuthorizer,
   Context
 } from 'aws-lambda'
 
@@ -30,7 +31,9 @@ const lambdaRunner = async (axiosConfig: AxiosRequestConfig, operation: Operatio
     .then((resp) => convertApiGwToAxios(resp, axiosConfig))
 }
 
-export const convertAxiosToApiGw = (config: AxiosRequestConfig, operation: Operation, crtLambdaContext?: Context): APIGatewayProxyEventV2 => {
+export interface LambdaRunnerAuthContext { 'lambda-invoke': true, callerIdentity: string }
+
+export const convertAxiosToApiGw = (config: AxiosRequestConfig, operation: Operation, crtLambdaContext?: Context): APIGatewayProxyEventV2WithLambdaAuthorizer<LambdaRunnerAuthContext> => {
   // extract path params
   // eg: for path template /v1/users/{id} & path url /v1/users/1108 -> will extract {'id': '1108'}
   const template = operation.path
@@ -61,7 +64,15 @@ export const convertAxiosToApiGw = (config: AxiosRequestConfig, operation: Opera
     headers[key] = val.toString()
   }
 
-  const lambdaPayload = {
+  // identify caller lambda
+  const sourceIdentity = ['lambda-invoke', crtLambdaContext?.invokedFunctionArn].filter(Boolean).join('-')
+
+  // default to lambda-invoke user-agent
+  if (!headers['User-Agent'] && !headers['user-agent']) {
+    headers['User-Agent'] = sourceIdentity
+  }
+
+  const lambdaPayload: APIGatewayProxyEventV2WithLambdaAuthorizer<LambdaRunnerAuthContext> = {
     version: '2.0',
     routeKey: '$default',
     rawPath: config.url,
@@ -75,7 +86,7 @@ export const convertAxiosToApiGw = (config: AxiosRequestConfig, operation: Opera
       authorizer: {
         lambda: {
           'lambda-invoke': true,
-          callerIdentity: crtLambdaContext?.invokedFunctionArn ?? 'lambda-invoke-not-specified'
+          callerIdentity: sourceIdentity
         }
       },
       domainName: 'lambda-invoke',
@@ -85,7 +96,7 @@ export const convertAxiosToApiGw = (config: AxiosRequestConfig, operation: Opera
         sourceIp: '',
         path: config.url,
         protocol: 'HTTP/1.1',
-        userAgent: 'lambda-invoke'
+        userAgent: headers['user-agent'] ?? headers['User-Agent']
       },
       requestId: crtLambdaContext?.awsRequestId ?? `lambda-invoke-${uuidv4()}`,
       routeKey: '$default',
@@ -94,9 +105,11 @@ export const convertAxiosToApiGw = (config: AxiosRequestConfig, operation: Opera
       timeEpoch: Date.now()
     },
     body: config.data ? JSON.stringify(config.data) : '',
-    isBase64Encoded: false,
-    httpMethod: config.method
-  } as APIGatewayProxyEventV2
+    isBase64Encoded: false
+  }
+
+  // for backwards compat with older event format
+  Object.assign(lambdaPayload, { httpMethod: config.method })
 
   debug('lambdaRequest %o', lambdaPayload)