To test the API in your local instance, you have the following pre-requisites:
1

Clone the cal.com repository

Please clone the cal.com repository. You can do it by following the instructions provided in Installation
2

Add license key in .env

Add a staging license key that goes in as value for CALCOM_LICENSE_KEY in your root .env file.You can use the following as staging license key
1a1f8138-0bfc-4f37-b4af-1e24fd145839
3

Start development server and create API key

Start the cal.com server using yarn dev on localhost and create the test API keys by visiting /settings/developer/api-keys
4

Copy .env.example file

Copy the .env.example file to .env file by running cp apps/api/v1/.env.example apps/api/v1/.envfrom root folder
5

Start API server and test API

Start the API server by running yarn workspace @calcom/api dev and start testing your API locally
By default, the app server runs on port 3000 and the API server runs on port 3003