# Social Launch Post

> Draft and cross-post a product launch announcement (with video/media) across X, LinkedIn, Threads, Bluesky, and Mastodon via the Typefully API -- the real request schemas, the presigned-upload gotcha, per-platform post-shape differences, and the honest limits of what's actually automatable (X blocks automated publishing of link-containing posts).

- Skill: `pooriaarab/social-launch-post` (Agent Skill)
- Install (CLI): `npx skillmds@latest add pooriaarab/social-launch-post`
- Raw SKILL.md: https://api.skillmd.com/api/skills/pooriaarab/social-launch-post/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: pooriaarab (https://skillmd.com/u/pooriaarab)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/pooriaarab/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:

```bash
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:

```json
{
  "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`](../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`](../ship-a-product/SKILL.md) — orchestrator this stage belongs to.