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Garfield 136bc257d1 docs: ChatGPT Custom GPT setup guide

- Step-by-step OAuth client registration
- OpenAPI schema import instructions
- Actions authentication config
- Troubleshooting table
- Tool availability status

2026-05-05 22:02:05 -04:00

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ChatGPT Custom GPT — Hermes MCP Setup Guide

Server: https://hermes.squaremcp.com

What you'll build

A Custom GPT in ChatGPT that can:

Send emails via your 7 accounts
Search and edit your Obsidian vault notes
Send WhatsApp messages (when credentialed)
Post to LinkedIn
Send Telegram messages
Post to Discord servers
Post to Instagram (when credentialed)

Step 1: Register an OAuth client

Hermes MCP uses OAuth 2.0 for ChatGPT authentication.

Run this curl to register a ChatGPT client:

curl -X POST "https://hermes.squaremcp.com/oauth/register" \
  -H "Content-Type: application/json" \
  -d '{
    "client_name": "ChatGPT Custom GPT",
    "redirect_uris": ["https://chat.openai.com/aip/[YOUR_GPT_ID]/oauth/callback"]
  }'

Save the response:

client_id
client_secret

Step 2: Get the OpenAPI schema

Your server's OpenAPI spec is live at:

https://hermes.squaremcp.com/openapi.json

ChatGPT will import this to know which endpoints are available.

Step 3: Create the Custom GPT

Go to chatgpt.com → Explore GPTs → Create
Configure:
- Name: Hermes Assistant
- Description: Your personal AI assistant with access to email, notes, and social media

Actions setup

Click Actions → Import from URL
Paste: https://hermes.squaremcp.com/openapi.json
Click Authentication → OAuth
- Client ID: (from Step 1)
- Client Secret: (from Step 1)
- Authorization URL: https://hermes.squaremcp.com/oauth/authorize
- Token URL: https://hermes.squaremcp.com/oauth/token
- Scope: email profile
- Token Exchange Method: Default (POST request)
Click Update to save the OAuth config

Privacy settings

Scroll to Privacy → toggle off if you don't want OpenAI training on your data

Step 4: Test the GPT

Ask your GPT:

"Send an email to team@fetcherpay.com saying the meeting is at 2pm"
"Search my Obsidian notes for 'funding strategy'"
"Post 'Hello world' to my LinkedIn"
"Send a Telegram message to Garfield"

Troubleshooting

Issue	Fix
"Authentication failed"	Re-register the OAuth client with the correct redirect URI
"Tool not found"	Check that the endpoint is listed in `/openapi.json`
"Unauthorized"	The GPT's token expired — re-authenticate in ChatGPT settings

Current tool availability

Tool	Status
Email (7 accounts)	✅ Ready
Obsidian vault	✅ Ready
LinkedIn profile/posts	✅ Ready (token deployed)
Telegram messaging	✅ Ready (token deployed)
Discord messaging	⚠️ Needs bot token
Instagram posts	⚠️ Needs Business Account setup
WhatsApp messaging	⚠️ Needs Cloud API number

Next: Discord bot token

If you want Discord working in ChatGPT too, create a bot:

discord.com/developers/applications → New Application
Bot tab → Copy Token
Deploy: kubectl set env deployment/hermes-mcp -n fetcherpay DISCORD_DEFAULT_BOT_TOKEN="your-token"

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