Hi there,
It was a documentation error for direct_messages/new to say rate limited: true – it’s not rate limited. Thanks for pointing that out.
Most POSTs on the API are to change or create data – to tweet, to retweet, to delete, to favorite, etc. All of these actions are not rate limited in the API but instead are account-based allowances that transcend the API.
Some of our information retrieval methods support both GET and POST, but they aren’t write operations. In the case of using a POST on one of the few “read” methods supporting it, the rate limit is essentially the same as if you were making a GET. They are the same API resource, you’re just calling it with a different HTTP method.
Some day in the future, write operations will likely also have rate limits and account “allowances” will become a concept of the past. At that time, write operations would include similar limit definitions as the read operations. Until then, you should just assume that the limits for write operations are always unknown to you.