PostOnce
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ChatGPT

Add PostOnce in ChatGPT

This page is for people on ChatGPT Plus, Pro, or Business who want PostOnce inside a conversation. Connected means you pasted the MCP URL under Developer Mode, signed in to PostOnce in the browser, and hit Allow. After that ChatGPT can list the accounts you already run and save unscheduled drafts. It must wait for a yes before publish or schedule. Never paste passwords, 2FA codes, refresh tokens, or API keys into the thread.

MCP URL

Streamable HTTP. ChatGPT should choose OAuth. Leave client id and secret empty.

https://postonce.app/api/mcp

How to add it

  1. Use ChatGPT on the web with Plus, Pro, or Business. Enterprise and Education work if an admin has allowed Developer Mode. The free tier cannot add a custom MCP server.
  2. Open Settings → Security and login and turn on Developer mode. Some accounts keep that toggle under Settings → Apps & Connectors → Advanced settings.
  3. Go to ChatGPT Plugins. The plus button creates a developer-mode app only after Developer Mode is on.
  4. Hit +. Name it PostOnce. Under Connection, paste the public MCP URL above, including /api/mcp.
  5. Choose OAuth. Do not paste a PostOnce API key. Leave the client id empty so ChatGPT can register against our authorize and token endpoints.
  6. Create the connection. Review the tools ChatGPT scanned. Sign in to PostOnce in the browser and hit Allow.
  7. In a chat, open the Plus menu, choose Developer mode, and select the PostOnce app for that conversation.

ChatGPT labels move. If you see “plugin with MCP URL” instead of Plugins, it is the same paste. The server URL does not change.

The plus button never appearing usually means the account is on the free tier, or Developer Mode is still off. A connection that fails on create is often the URL without /api/mcp. If the app exists but the model says it has no PostOnce tools, the conversation does not have the developer-mode app selected in the Plus menu.

After you connect

Ask ChatGPT to list your PostOnce accounts first. Then ask for an unscheduled draft, read the copy and the targets, and say yes only when you want it scheduled or published. If Instagram or TikTok is missing, ChatGPT should send you to postonce.app/accounts and stop. Provider consent for those networks happens there. The model must not ask for passwords, 2FA codes, refresh tokens, or API keys in the thread. Hosted MCP can pull a public image or video URL onto the PostOnce CDN; files dropped into the ChatGPT thread still cannot.

Prompts that work in a ChatGPT thread

Paste these after the PostOnce app is selected for the chat. Say no if the model offers to publish.

  • “In this chat, use the PostOnce developer-mode app only. List my PostOnce accounts.”
  • “Who am I signed in as on PostOnce, and what plan is this workspace on?”
  • “Create an unscheduled PostOnce draft that says “Tuesday studio hours, 10–2” for an Instagram account I already connected. Do not publish or schedule.”
  • “Show the draft you just saved in PostOnce. Do not schedule it and do not publish it.”

Directory listing

Lucro Limited business verification has been submitted. A public ChatGPT Apps / Codex Plugins directory listing is not live, so you will not find PostOnce by browsing the directory. You add the MCP URL yourself, as above. The domain-challenge file at /.well-known/openai-apps-challenge stays 404 until OpenAI issues OPENAI_APPS_CHALLENGE.

Price

PostOnce Solo is €15/month, or €12/month billed yearly (€144/yr). Pro is €30/month, or €25/month billed yearly (€300/yr). Those are VAT-inclusive list prices: no per-channel fee, no free plan, and signup is Lemon checkout.

Buffer Essentials is $6 per channel monthly, or $5 per channel if billed yearly, so five connected accounts is $30/month on monthly Buffer ($25/month effective yearly). Post Bridge's public Creator plan is $29/month for 15 connected accounts. Solo at €15/month sits against Post Bridge Creator at $29/month, and against Buffer at $30/month for five channels. Those figures are EUR and USD as published.

PostOnce pricing

Other clients

Same server for Grok, Cursor, and Claude. Technical fields live on the MCP connect page.

Stuck? Email [email protected]. Privacy · Terms

Lucro Limited, Ireland. Company no. 811725.

Questions: [email protected]

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