Grok + PostOnce

Turn a Grok conversation into a social post

Connect Grok to PostOnce to find your social accounts, prepare image drafts, and publish posts you approve.

Requires PostOnce Creator or Pro and permission to add a custom connector in Grok. No PostOnce API key is needed. This manual OAuth setup is not an approved directory listing. Publishing requires a connected destination; the setup scopes cover accounts and posts, not workflow management or media uploads.

See setup steps

Set up your connection

Connect Grok to PostOnce

Before you connect

Sign in to Grok with permission to add a custom connector. In a Business or Enterprise workspace, an administrator first provisions it in the xAI console. This setup uses Grok chat, separate from Grok Bot, Grok Build and the xAI developer API.

You need PostOnce API access on your plan. Your actual entitlement is checked when you authorize access. You can connect the assistant and check your accounts before connecting a social account; a connected social account is required to publish.

Connect social accounts Check PostOnce plans Check Grok availability

1
Add a custom connection in Grok
Open Plugins → Connectors → New Connector → Custom. Enter PostOnce as Name and the remote MCP URL below as Server URL. Select Add Connector to open OAuth Credentials Required.
Remote MCP server URL
```
https://postonce.to/mcp
```
Name
PostOnce
Description
Publish posts and manage automatic crossposting with your connected PostOnce accounts.
Authentication
OAuth · public client with PKCE
Copy the public client ID and endpoints below into the matching fields. Leave Client Secret empty and keep Token Auth Method set to none (PKCE only, recommended). Add each scope separately and press Enter after each one. These scopes allow account discovery and draft/post actions. If you also need workflow tools, add workflows:read and workflows:write during setup. Signed media uploads separately require media:read and media:write. Authorize only the actions you need. No PostOnce API key is needed.
Client ID
```
_UIxpQLv_nCpfAt6XCvyCMlqzVLTpRv97uGYz61kWx-
```
Authorization Endpoint
```
https://postonce.to/api/oauth/auth
```
Token Endpoint
```
https://postonce.to/api/oauth/token
```
Scope 1
```
offline_access
```
Scope 2
```
accounts:read
```
Scope 3
```
posts:read
```
Scope 4
```
posts:write
```
Open Grok
2
Sign in and review access
The connection opens PostOnce’s sign-in and consent flow on postonce.to. Check the signed-in account, app name, return destination, and listed permissions. Select Allow access to continue, or Cancel to stop. A plan restriction must be resolved in PostOnce before authorization can complete.
Complete the OAuth form and sign in to PostOnce when it opens. In a Grok chat, open Attach → Connectors and enable PostOnce before trying the account prompt below. If Grok requires account details before your first chat, complete its account setup using your own information.
3
Verify with an account check
Try this prompt
Show my connected social accounts.
Look for a PostOnce tool result with your actual account names and IDs. A successful empty result confirms the account check worked, but there are no connected accounts to publish to. Connect a social account in PostOnce before publishing, then ask again. Adding the server alone does not prove authorization or publishing succeeded.
Choose your accounts and confirm the intended post before publishing. Inspect its returned post ID and each destination’s status; queued does not mean delivered.
Review published posts
4
Create and review an unpublished draft
First image draft
Create an unpublished PostOnce draft with the caption "Trying my first Grok draft" and this public PNG image: https://postonce.to/integrations/assets/postonce-transparent.png. Leave destinations empty and do not schedule or publish it. Return the draft ID, then get that draft and show me its saved caption, image, and status for review.
Check that the returned draft stays in your inbox with the image, caption and no destinations. You can review it in PostOnce before choosing accounts or publishing. This example uses a public image URL; it does not upload a Grok chat attachment.
Review your drafts in PostOnce

Reconnect or revoke access

In Grok, open Plugins → Connectors → PostOnce → Reauthenticate, then sign in to PostOnce and review access again. After reconnecting, request a fresh account or draft read; a previous chat response does not verify the new connection. To disconnect, open Preferences → AI agents → Connected apps in PostOnce and revoke the matching app. Remove the connector from Grok as well if you no longer want it listed.

The hosted connection cannot read a path on your computer or assume access to a chat attachment. Use a supported public media URL or a documented client upload flow.

Read Grok’s connection instructions

Optional · after connecting

Add the PostOnce workflow skill

Give Grok reusable guidance for choosing accounts, preparing media, publishing, and checking delivery. The skill adds instructions; it does not connect your account, grant permissions, or change plan access.

Read the PostOnce skill. In Grok, open Plugins → Skills → New Skill → Write skill manually. If a skill named postonce already exists, review it and preserve your custom instructions before making changes.
In Name, enter the file’s name value: postonce. In Description, copy the description value from the metadata between the opening --- lines, without the field name. In Instruction, copy everything from # PostOnce through the end of the file. Leave the opening metadata out of Instruction, then select Save.
Open the saved skill and select Try it now. Keep your PostOnce connector enabled and ask Grok to use the skill to show your connected accounts or review an existing draft. Expand the response’s activity and check for Loaded skill postonce and a fresh PostOnce tool result.

From connection to first result

Start with one useful action

Find your accounts

Try this prompt

Show my connected social accounts.

Use the returned names and IDs to choose your targets. If nothing appears, connect an account in the dashboard.

Publish an update

Try this prompt

Help me publish a product update. First show my connected accounts, then ask me to choose the destinations and confirm the exact text before publishing.

After creation, ask for the post ID and each destination’s delivery status. A queued post is still waiting to publish.

Set up crossposting

Workflow actions require workflows:read and workflows:write. Include these scopes when setting up your Grok connector and approve them in PostOnce. The default account/post scopes above do not allow this example; reauthenticating without adding scopes will not expand access.

Try this prompt

Show my connected accounts and the available crossposting options. Help me choose a supported source and destinations, then confirm the workflow before creating it.

A created workflow applies to future matching source posts. Inspect the workflow in PostOnce before relying on it.

Review posts in PostOnce Review crossposting workflows

Know what your agent can access

Connected accounts and scoped actions

PostOnce uses the permissions you approved during consent and your existing account permissions. Your available destinations come from your connected accounts; media and text requirements still vary by platform.

Media needs a supported upload path

The hosted server cannot read a file path on your computer or assume access to a chat attachment. For a first media post, use a supported publicly accessible media URL and have the agent validate the selected platform’s requirements before publishing.

Media post example

Help me publish an image from a public media URL. Ask me for the URL, text, and connected destination accounts; check the platform requirements and confirm the post before creating it.

Questions before connecting

Do I need a particular PostOnce plan?

You need PostOnce API access on your plan. Your entitlement is checked during sign-in and consent. Connecting an assistant does not change your plan.

What if my agent shows no social accounts?

A successful empty account result means the connection worked. Connect or reconnect a social account in PostOnce before publishing, then ask again. Check that you authorized the intended PostOnce account and accounts:read permission.

How do I check a failed or queued post?

Ask the agent to get the post using its returned ID and inspect each target’s status and error. Review the post in the dashboard. Check the existing result before creating another post to avoid duplicates.

How do I disconnect or reconnect?

Revoke the matching app in Preferences → AI agents → Connected apps and remove the connection from your assistant. To reconnect, start its Connect flow again and review the requested permissions.