docs: ChatGPT Custom GPT setup guide

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

CHATGPT_SETUP.md

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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:
+
+```bash
+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
+
+1. Go to [chatgpt.com](https://chatgpt.com) → **Explore GPTs** → **Create**
+2. Configure:
+   - **Name:** `Hermes Assistant`
+   - **Description:** `Your personal AI assistant with access to email, notes, and social media`
+
+### Actions setup
+
+3. Click **Actions** → **Import from URL**
+4. Paste: `https://hermes.squaremcp.com/openapi.json`
+5. 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)`
+
+6. Click **Update** to save the OAuth config
+
+### Privacy settings
+
+7. 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:
+1. [discord.com/developers/applications](https://discord.com/developers/applications) → New Application
+2. Bot tab → Copy Token
+3. Deploy: `kubectl set env deployment/hermes-mcp -n fetcherpay DISCORD_DEFAULT_BOT_TOKEN="your-token"`