Social Launch Post

social-launch-post

Empirical, from actually posting a real launch announcement with an attached video across 5 platforms via Typefully's v2 API.

1. Core flow

POST /v2/social-sets/{social_set_id}/drafts   -> creates a draft (omit publish_at to keep it a draft)
PATCH /v2/social-sets/{social_set_id}/drafts/{draft_id}  -> update platforms/content on an existing draft

GET /v2/social-sets (no id needed) lists the accounts your API key can post as — grab the right id from there before doing anything else if there's more than one connected account/brand.

Auth: Authorization: Bearer $TYPEFULLY_API_KEY on every call.

2. Media upload is a 3-step dance, and the PUT step is a real trap

1. POST /v2/social-sets/{id}/media/upload with {"file_name": "..."} → returns {"media_id": "...", "upload_url": "<presigned S3 URL>"}.
2. PUT <upload_url> with the raw file bytes.
3. GET /v2/social-sets/{id}/media/{media_id} → poll until "status": "ready".

Step 2 fails with SignatureDoesNotMatch (403) if you send ANY extra headers — no Content-Type, no re-declaring the x-amz-meta-* values as headers (they're already baked into the presigned URL's signed query string; sending them again as headers doesn't match what the server actually signed). The working call is exactly:

curl -X PUT -H "Content-Type:" --data-binary "@file.mp4" "<upload_url>"

The empty -H "Content-Type:" is deliberate — it tells curl to omit the header entirely, since curl otherwise attaches a default that doesn't match the presigned signature. Three earlier attempts (default content-type, matching content-type explicitly, re-sending the meta headers) all failed identically; the fix was sending nothing extra at all.

3. Attaching media and building the platform payload

Attach a ready media_id to a post via the media_ids array field on that post object:

{
  "platforms": {
    "x": {
      "enabled": true,
      "posts": [
        {"text": "hook line here", "media_ids": ["<media_id>"]},
        {"text": "follow-up / link, as a reply in the thread"}
      ]
    }
  }
}

Per-platform post-shape differences are real, not just theoretical:

• LinkedIn only supports a single post, not a thread — sending a 2-element posts array to linkedin fails validation ("LinkedIn only supports single posts"). Combine hook + link into one post's text for LinkedIn specifically; keep the thread structure for X/Threads/Bluesky/Mastodon.
• Enable multiple platforms in the same PATCH by adding each as its own key under platforms — reuse the same thread-shaped posts array for the platforms that support threads, and a separate single-post array for LinkedIn.

4. Publishing is not fully automatable on X

Setting {"publish_at": "now"} via the API can return {"error": {"code": "FORBIDDEN", "message": "This is not allowed by X policy. Direct publishing of X drafts containing URLs is blocked."}}. This is a real anti-spam/anti-automation policy enforced server-side by Typefully on X's behalf — it applies identically regardless of which client hits the API (REST or an MCP wrapper share the same backend check), so there's no legitimate way around it via API. Don't try to route around it (splitting/obfuscating the URL, posting the link in a follow-up edit, etc.) — that's evading an anti-spam control, not solving a technical problem. The correct move: leave the draft ready via the API, and have the human publish it manually through Typefully's own UI, which is designed to satisfy whatever additional human-in-the-loop step X's policy requires.

5. Video aspect ratio for cross-posting

A launch video built at 1:1 (square) — the natural choice if the storyboard/generation pipeline (launch-video-generation) was built that way — will get pillarboxed (black bars) in vertical-feed players expecting 9:16. Two fixes, and the plainer one is usually the better call:

• Crop/pad to 9:16 with a blurred background fill (ffmpeg gblur on an upscaled+cropped copy of the same footage as background, original square centered on top): technically fills the frame edge-to-edge, but the blurred top/bottom bands read as visually noisy and can look worse than the plain original, not better.
• Just keep it square. A 1:1 video posts natively without modification on X/Threads/Bluesky/LinkedIn feeds; pillarboxing on vertical-only surfaces (e.g. a Stories/Reels-style placement) is a smaller cost than an unwanted blur treatment. Prefer this unless the target surface is specifically vertical-only.

See also

• ../launch-seo/SKILL.md — run this before posting: without Open Graph/Twitter Card meta on the linked site, the posts this skill drafts will unfurl bare (no title, description, or image) across every platform.
• ../ship-a-product/SKILL.md — orchestrator this stage belongs to.