Apologies, I didn’t notice you were referring to the signals API
From the signals docs:
To use the API, the user needs an API KEY or TOKEN that will pass along the request. Users need to sign up to get it.
This API KEY restricts the API. The access is limited to 40000 API requests per day. If the user exceeds that limit in 24 hours, the service will return a 429 HTTP status code. If the users need to make more requests, they should consider contacting us and tell us why they need a higher quota. It is possible to know in real-time the quota consumed daily from the Main page.
There is also an ANONYMOUS PLAN. The platform applies this plan if a developer does not pass any API TOKEN when making a request. So any user can test the API before signing up!
If you are not passing a token it should only be used for testing. The free plan on the other hand (you must sign up), allows 40000 hits/day. The amount of hits being defined based on the endpoint.