Automate Cross Posting With Make: A Creator OS API Build Guide

If you want to automate cross posting with Make, you can build a scenario that watches for new content and fans it out to every network from a single HTTP module. This guide walks through the whole build: choosing a trigger, configuring the HTTP module, calling the Creator OS REST API, parsing the response, and fixing posts that fail partway through. It is the deep version of the roundup we published on posting to all social media at once, where a scenario like this only got a paragraph.

[Trigger]                 [Router]              [HTTP module]
New RSS item  ---------->  branch: blog   ----->  POST /v1/posts
New upload    ---------->  branch: youtube -----> POST /v1/media
Webhook       ---------->  branch: default -----> POST /v1/posts
                                     |
                                     v
                           [Response: post_ ids,
                            missing_platforms]

One trigger, one HTTP module, one API call per piece of content.

Why Make Beats Manual Cross Posting (and Where It Still Falls Short)

The manual loop is familiar. You write a post, open Instagram, paste it, fix the line breaks, open TikTok, paste it again, then wonder whether the LinkedIn version should have the link in the caption or the first comment. Make removes the repetition. A scenario runs on a schedule or a webhook and fires the same steps every time, so the tenth post costs you nothing extra.

What Make does not do on its own is understand the platforms. A visual automation builder passes data between modules. It does not know that a TikTok photo post needs a cover index, that Instagram captions cannot hold clickable links, or that the same video needs different handling on Shorts than on Reels. That knowledge has to live somewhere. In this build it lives in Creator OS, because the API applies each platform’s rules for you when you name the networks in a post.

The practical difference: Make is the scheduler and the glue, Creator OS is the publishing engine. If you would rather skip Make entirely, the hosted MCP server lets an AI app call the same tools directly, and the walkthroughs live on the KevBuildsApps YouTube channel.

What You Need Before You Build: Creator OS API Key, Connection and Modules

Three things first.

A Creator OS API key, the kind that starts with cos_live_. Keys are pinned to one workspace, which is one set of socials. An agent or scenario holding one workspace’s key cannot post to another workspace. If you want a scenario that is allowed to read but never publish, read read only API keys for AI agents and use a read-only connection instead.
A Make account with the HTTP module available, plus whichever trigger app you pick (RSS, YouTube, or a webhook).
Connected accounts in Creator OS. Run creatoros accounts:list and creatoros accounts:health locally before you build anything. A scenario that fans out to seven networks will fail loudly if one token is stale, and it is easier to fix that in the terminal than inside a scenario run log.

The base URL for the REST API is in the docs at https://www.creatoros.ca/docs. Read it there rather than hardcoding something from a forum post.

Scenario Design: One Trigger, One Router, Seven Networks

Keep the scenario boring. One trigger. One router. One HTTP module per content type. Do not build seven HTTP modules, one per network. The whole point of the Creator OS POST /v1/posts endpoint is that you name the platforms once and it handles the per-network rules.

Here is the shape that works:

Trigger fires. You get a title, a body, a URL, maybe a media URL.
Router sends the bundle down one of a few branches: blog article, YouTube upload, or default.
Each branch sets a handful of variables (caption text, platform list, media list, schedule timezone).
A single HTTP module posts to /v1/posts.
A filter or a final step checks missing_platforms in the response and alerts you.

That last step is the one most builds skip, and it is the reason people think fan-out automation is unreliable. It is not unreliable. It is just unreported.

Trigger Option A: New Blog Post via RSS or Webhook

The simplest trigger is an RSS feed from your blog. Point Make’s RSS module at your feed and set it to watch for new items on a schedule. This is a good fit if you publish on a WordPress site connected to Creator OS, since Creator OS writes SEO articles and keeps them as drafts by default unless publishing is set. Read the docs for the blog connection details.

The cleaner trigger is a webhook. Creator OS sends post.published, comment.received and other events, signed with an X-CreatorOS-Signature header. You can list and create them from the terminal:

creatoros webhooks:create --url https://hook.make.com/your-scenario-id \
  --events post.published,comment.received

Use creatoros webhooks:test <id> to fire a sample payload into the scenario before you trust it. If your scenario verifies the signature, this is also how you catch a mismatch early instead of at 11pm on a launch day.

Trigger Option B: New YouTube Upload via the Data API

If your content starts as video, watch your own channel for new uploads. Make has a YouTube module, and you can either poll for new videos or use a push notification. Keep in mind that YouTube’s quota is the constraint that bites people here, and the fix is usually to poll less often and cache what you already processed. There is a longer explanation in our post on the YouTube Data API upload quota.

Once the trigger fires, you have a video URL, a title, and a description. That is enough for a fan-out bundle. A video uploaded as a vertical short becomes a Short automatically through the Creator OS YouTube path, and firstComment is posted and pinned, up to 10,000 characters, so you can drop your links there instead of stuffing the description.

Calling the Creator OS REST API From a Make HTTP Module

This is the part worth getting exactly right. The simple form of POST /v1/posts takes a flat body:

{
  "content": "New build guide is live. Link in the first comment.",
  "platforms": ["instagram", "tiktok", "youtube", "twitter", "linkedin", "facebook", "threads"],
  "media": ["med_abc123"],
  "schedule_at": "2026-03-04T15:00:00Z",
  "timezone": "America/Toronto",
  "post_type": "reel",
  "firstComment": "Full walkthrough: https://example.com/guide"
}

Two things to note. First, media accepts a med_ id or a URL. Upload a file once with POST /v1/media and reuse the returned id on every network, which saves you from re-uploading the same 80MB file seven times inside a Make run. Second, the advanced form exists when you need per-network differences. In that form, platforms becomes a list of objects with platform, account_id, options and content, and TikTok settings go in a top-level tiktok object.

Watch the platform quirks your scenario touches. Instagram captions have no clickable links, so use firstComment for the URL, and note that the API cannot attach trending audio, so any sound has to be baked into the file. TikTok requires privacy_level, allow_comment, allow_duet, allow_stitch, and both consent flags, though the simple post form fills those for you. Details are in the post options docs.

For a caption coming out of a generator step, check the length before you send it:

creatoros validate:post-length --text "$(cat caption.txt)"

Threads caps a post at 500 characters, and this saves you from a failed branch after the router has already run.

Parsing the Response and Handling Rate Limits and Failures

Responses come back with opaque typed ids: acc_, post_, cmt_, conv_, msg_, auto_, med_. Store the post_ ids in your data store. You will want them later for analytics and for editing text after publishing on the platforms that allow it.

Two fields matter for error handling:

missing_platforms lists any network named in the post that is not connected. The rest of the post still goes out. Do not treat this as a hard failure. Treat it as a to-do.
Errors use one shape: { "error": { "code": "...", "message": "...", "status": 400 } }. Parse that consistently in a Make error handler so your logs read the same way every time.

On rate limits, the safe pattern for a fan-out scenario is a small sleep between branches when you have several pieces of content queued at once, plus retries with backoff on 5xx responses. Do not retry a 4xx. A rejected caption will be rejected again.

If a post goes out on some networks and fails on others, that is a mid-fan-out failure and the tool for it is creatoros posts:retry <postId>. You can also pull state with creatoros posts:list --status failed and creatoros posts:get <postId> to see exactly which branch got stuck.

Testing, Logging and Fixing Posts That Fail Mid-Fan-Out

Build the scenario in this order, and do not skip steps.

Dry run the payload. Create one draft post from the terminal first: creatoros posts:create --text "test" --platforms instagram,tiktok --draft. If that works, the API key and workspace are fine and any later problem is Make’s mapping.
Turn the scenario on with one branch only. Send the blog branch to a single network. Confirm the response contains a post_ id.
Add networks one at a time. This tells you which network rejects the payload rather than getting one opaque failure across seven.
Log every response body. Make’s run history keeps input and output per module. Keep it. When something odd happens three weeks later, that history is the only record.
Add an alert on missing_platforms. A Slack or email step here catches a disconnected account before you notice a network has been silent for a week.

For the platforms where replies matter, the same scenario pattern extends. Comment replies work on Instagram, Facebook, X, Threads, YouTube and LinkedIn, and DMs work on Instagram, Facebook and X. If you want an auto-reply loop with keyword triggers, the automation shape is creatoros automations:create with an optional --commentReply. There is more on the reply side in automating Instagram and TikTok replies, including the fact that TikTok comment replies are not supported, only hide and delete on TikTok for Business accounts.

If you prefer connecting your AI app directly to Creator OS instead of routing through Make, the hosted MCP server supports Claude, ChatGPT, Claude Code, Cursor, Codex, Windsurf and VS Code. The setup for one of those is covered in Windsurf MCP setup for social media posting, and the tool names you would call include create_post, list_posts, get_post_analytics and ads_boost_post.

Get Started: Wire Your First Scenario and Claim Your API Key

Start with one branch and one network. Get a post_ id back. Then add the other six. The API keys, the MCP server, the CLI and the agent skills are included in every plan, and the Creator plan is $19.99/month or $59.99/year for up to 8 connected accounts, which is 7 socials plus Skool. Read the API reference at https://www.creatoros.ca/docs for the base URL, request shapes and the full webhook event list, then watch the build on the KevBuildsApps channel.