Tumblr is older than most of the networks here and its API shows it in a good way: a post can be nearly any length, carry thirty pictures, and be read back by anyone with an API key. Preflight publishes text, pictures and video to your primary blog in Tumblr's Neue Post Format, turns a last line of hashtags into tags, and reads the notes.
| Tumblr through Preflight | What the API allows |
|---|---|
| Text limit | 250,000 characters |
| Media | Pictures and video, up to 30 files |
| Pictures | Up to 20 MB each |
| Video | 500 MB, up to 10 min |
| Thread in one go | No |
| First comment | No |
| Alt text | Yes |
| Edit after publishing | No, the API has no edit |
| Delete from Preflight | Yes |
| Comments | Read only |
| Figures reported | likes, shares, comments |
| Retention and traffic sources | No |
What goes out
A post of text, up to 30 pictures or one video, in the block format Tumblr renders natively. Hashtags written on the last line of the post become the post's tags rather than staying in the body, which is how a caption shared with Instagram lands on Tumblr the way Tumblr expects. Pictures take alt text. Tumblr has no character limit of its own worth naming; a post is split into blocks and may run to about a megabyte, and Preflight holds it to a quarter of a million characters as a sanity ceiling.
Connecting a blog
Connect with Tumblr. Preflight asks for basic access, writing and an offline token so the connection does not expire between posts. One connected account is one blog, the member's primary one; a secondary blog is a second connection, because Tumblr's tokens for the same user otherwise invalidate one another.
What is checked before publishing
Pictures are JPEG, PNG or GIF up to 20 MB; one video of up to 500 MB and ten minutes; two videos in one post are refused, because Tumblr takes one. More than 30 pictures are warned about as dropped. At publish time, two of Tumblr's own answers are handled rather than failed: a blog that has reached its daily posting limit is retried later, and a blog still processing an earlier video is retried shortly, with the post's row saying which. The same checks run on a post sent through the public API or the MCP server.
What the API will not do
A published post cannot be edited from Preflight; it can be deleted. Notes, which are Tumblr's likes, reblogs and replies, are read and shown as figures, with the app's own key rather than your token, so reading them never spends the calls publishing needs; the replies themselves are read but not answered. Reblogging and asks are not part of publishing and are not offered.
How the files travel
Tumblr takes the bytes from Preflight rather than fetching a URL, so every picture and the video go through the upload worker and are counted against your plan's storage like any other file. A video is accepted by Tumblr and then processed on its side, which is why a second video to the same blog within a few minutes is told to wait rather than failed; the post row shows the wait and the retry.
In the API
Tags, alt text and the file rules are the same through the API and the MCP server, and the last-line rule for hashtags applies to a post an agent writes too. Tumblr is on every plan at pricing, including the free one.
Questions people ask
- How do hashtags become Tumblr tags?
- Write them on the last line of the post. Preflight removes that line from the body and sends the words as the post's tags, which is how Tumblr shows and indexes them.
- Can Preflight post to a secondary Tumblr blog?
- Each connection is one blog, the account's primary one. Connect again for a secondary blog; Tumblr's tokens for the same member would otherwise invalidate each other.
- Can I edit a Tumblr post after publishing?
- Not from Preflight. A published post can be deleted and posted again; editing in place happens on Tumblr itself.