Create a social media post: schedule it (explicit time or next free slot), publish immediately, or save it as a draft. Media must be public URLs — use upload_media first for reliable hosting. Media is REQUIRED for Instagram, TikTok, YouTube and Pinterest, except for drafts. Instagram: one photo is a feed post, one video a Reel, and 2 to 10 files (photos and videos, in order) a carousel whose photos are all cropped to the first photo's shape. Facebook Pages take up to 10 photos in one post, or one video. LinkedIn posts one MP4 video alone, or turns 2 to 20 photos into a carousel (a PDF document, one page per photo, all cropped to the first photo's shape, titled with the first line), and posts a PDF URL as a document. Pinterest also requires pinterestBoardId (use list_pinterest_boards), and takes one image or one MP4/MOV video; an image sent with the video becomes its cover. YouTube publishes one video; an image sent with it becomes its custom thumbnail (JPG or PNG, 1280x720 works best; YouTube only takes custom thumbnails from verified channels, and the video is published without one otherwise). WordPress, Ghost, Dev.to and Hashnode publish an article: the first line of content is its title, the rest the body in Markdown, the first photo the cover image (Dev.to and Hashnode don't take videos; Hashnode needs Hashnode Pro on the blog). Tumblr posts the text with up to 30 photos or one video. articleSettings sets their tags, canonical URL, draft, Ghost newsletter and Dev.to AI disclosure. Google Business Profile posts a "What's new" update on the location: up to 1,500 characters and one photo (no video), with an optional button set in googleBusinessSettings. scheduledAt is interpreted in the workspace timezone.