Automating REST API Functionality Testing

I'm seeking an experienced developer versed in API testing using existing tools such as JMeter and others. The project focus is on API testing automation and the key aim here is to ensure API functionality. Scope necessary for the role includes:

- Configure an existing tool to test all of our API endpoints.
- Checking and guaranteeing the functionality of the API.
- Proficiency in at least one API testing tool

The API in question is used as a files check layer before uploading to S3. The users can upload files, list, download, and more. The API allow synchronous requests and async requests.
We need to automate the testing in order to answer the following questions.

- Are all the endpoints of the API working?
- How much time is taking every endpoint (average time maybe)?
- What was the output of the tested endpoints?

Experience in API testing is preferred. A meticulous approach to testing and a keen eye for detail will be invaluable for this project.

Please include what tool will you use and your approach in the proposal.

Thanks!