Running AUTOMATIC1111's Stable Diffusion API on Mac

Question

I'm trying to incorporate the stable diffusion service using AUTOMATIC1111's Stable Diffusion Web UI API, whose documentation is written here

As suggested by the documentation, I sent a post request using the URL

http://127.0.0.1:7860/sdapi/v1/txt2img

with a simple request body

{
    "prompt": "a puppy on moon",
    "steps": 5
}

Then I received the result

{
    "detail": "Not Found"
}

I assume the endpoint has received my request. What is going wrong here?