Grok: Create and Publish Social Media Posts

Grok can go from one sentence to a drafted X, Instagram or LinkedIn post with a generated image. What it needs is two connectors next to it: a media generator (fal.ai or Higgsfield) and a publishing tool. PostSider is the publishing tool I built for exactly this, so this guide uses it.

The idea is the same as in my Claude version. What is specific to Grok is the connector page, the public-URL rule, and Grok Bot, which turns the flow from a chat into something closer to a teammate.

Grok plans, the generator renders, PostSider delivers

Grok decides what to post and writes the captions. fal.ai or Higgsfield turns the prompt into a file. PostSider holds the social accounts, the queue and the network rules.

Notice that X is just one of the destinations. Grok lives next to X, but publishing to X through PostSider works the same as publishing anywhere else, and the same post can go to LinkedIn and Instagram in one call.

Add three custom connectors

Open grok.com/connectors, click New Connector, choose Custom, paste the MCP server URL and finish the sign-in that server asks for. Grok then discovers the server’s tools.

Repeat it for each server:

Connector	URL to paste	Sign-in
PostSider	https://mcp.postsider.com/mcp	PostSider account (OAuth)
fal.ai	https://mcp.fal.ai/mcp-relay	fal account
Higgsfield	https://mcp.higgsfield.ai/mcp	Higgsfield account (uses plan credits)

You need only one of the two generators. Pick fal.ai if you want pay-per-run pricing and a huge model list, Higgsfield if you already create video there.

Three things trip people up:

• The URL must be public. Grok connects from xAI’s servers, so localhost and private addresses are rejected (xAI’s tunneling note). The three hosted URLs above are fine as they are.
• Teams go through the console. On Business and Enterprise, an admin adds the custom server in the xAI console first (connector management), and then each member connects their own account.
• Plan tier. Third-party guides report that custom connectors on grok.com need a paid tier. If you do not see Custom, that is the likely reason.

Test before you create anything: “List my PostSider channels.” If Grok answers with your real accounts, publishing works. Then ask the generator for one test image.

Use the generator connector, not Grok’s built-in images

PostSider needs a file it can download from a public HTTPS link. A connector like fal.ai or Higgsfield returns one. An image Grok draws inside the chat may not.

So name the tool in your prompt: “generate it with fal.ai”. Grok then calls the connector, gets back a URL, and passes that URL to postsider_upload_media_from_url. PostSider copies the file into its own media library and returns an id and path for the post.

That copy is the point. Generator links are short-lived delivery links; every fal result I pulled while writing this came with a note that source URLs may expire. A post that sits in the queue until next week has to point at PostSider’s copy, not at the generator.

Grok Bot: the same flow as a weekly routine

Grok Bot is xAI’s always-on agent. It has its own cloud computer, uses the same connectors as plugins, and can be reached from the Grok apps and Slack. That makes it a good fit for recurring content work.

xAI’s Team Bots docs list a plugin type for a custom remote HTTPS MCP server, which is how PostSider and fal.ai plug in. On teams, the MCP allowlist that controls which servers Bots may use is an Enterprise feature.

Here is an illustrative routine I would give a Bot:

The pattern behind it is the one I describe in agent drafts, queue ships: the agent fills the queue with drafts, and the queue, not the agent, decides the exact times.

The seven steps under every Grok request

Whether you type in the chat or a Bot runs on a schedule, every post goes through the same tool calls:

1. Brief: what the post is for, which networks, when.
2. Generate: fal.ai or Higgsfield returns a file URL.
3. Review: you approve the media (in chat, or later in PostSider for Bots).
4. Store: postsider_upload_media_from_url returns an id and path.
5. Rules: postsider_get_channel_rules per channel. X needs who_can_reply_post, Instagram a post_type, TikTok a privacy level, YouTube a title.
6. Create: postsider_create_post as draft, schedule or now.
7. Read back: postsider_get_post confirms what was saved.

One warning for TikTok: PostSider publishes there with direct posting, so a scheduled TikTok post goes live when it fires, with no TikTok inbox in between. Review before it is scheduled.

For the file format limits and a cost chart of fal.ai models, see the Claude guide.

Prompts that work in Grok

Name the connectors and the post type, and Grok picks the right tools.

Generate a 16:9 image with fal.ai for this X and LinkedIn post: CAPTION.
Minimal, black and white, no text in the image. Show it first.
If I approve, use PostSider: store it, check the X and LinkedIn rules
(replies: everyone), and create both as DRAFTS for TOMORROW 08:00 my time.

Make a 5 second vertical 9:16 MP4 with Higgsfield showing PRODUCT.
After I approve, create PostSider drafts for TikTok and Instagram Reels
with these captions: CAPTIONS. TikTok privacy: public. Do not schedule.

Start with one draft

Add PostSider and one generator at grok.com/connectors, make one image, and get one draft into your calendar. Then hand the routine to a Bot.

You can try PostSider for free and connect your first social media account in a few minutes. The tool reference is in the PostSider MCP docs.