TextService:FilterStringAsync() failing with HTTP 429 error

It seems that Roblox’s mandatory text filtering system has an upper limit on the length of a string. When I send a very large string in a custom chat system that I wrote, I get the following error in the server log:

Now I’m only sending one request to the service, but I’m getting this warning. Does anyone know what the upper limit is on text filtering? It’s not in the documentation.