nessie

Connect ChatGPT, Claude and other AI apps

Add Nessie to ChatGPT, Claude, Claude Code or any MCP client, and choose what it may do as you.

The address

Every AI app connects to Nessie at one address:

https://nessie.works/mcp

That is all any of them needs. Signing in, registering the app and choosing what it may do all happen in Nessie, on a screen that names the app and where it will send you back to. You never copy a key or a token.

https://api.nessie.works/mcp is the same server at its API address, the one Nessie shows under Settings › Security; either works. Running Nessie yourself? Use your own API address with /mcp on the end.

ChatGPT

  1. Open ChatGPT Plugins, select the plus button, then Add custom MCP server.
  2. Name it Nessie, and under Connection enter https://nessie.works/mcp.
  3. Choose OAuth for authentication. ChatGPT registers itself with Nessie; there is nothing else to fill out.
  4. Confirm the warning about custom servers, then Create as a plugin.
  5. ChatGPT opens Nessie. Sign in if you are asked, choose what it may do, and press Allow.

Whether you can add a custom server depends on your ChatGPT plan and, in a company workspace, on what its admins allow. OpenAI moves these controls from time to time; if yours look different, follow OpenAI’s current steps with the address above.

Claude

In claude.ai, the desktop app or the mobile app:

  1. Go to Customize › Connectors and select Add custom connector.
  2. Enter https://nessie.works/mcp as the server URL. Leave the OAuth client ID and secret empty.
  3. If Claude asks how it should identify itself, choose Register automatically.
  4. Select Connect. Claude opens Nessie, where you choose what it may do and press Allow.

On a Team or Enterprise plan an Owner adds the connector once, under Organization settings › Connectors, and each person then connects it with their own Nessie account. Anthropic’s guide: Add a connector that isn’t in the directory.

Claude Code

claude mcp add --transport http nessie https://nessie.works/mcp

Then run /mcp in a session and choose to authenticate; Claude Code opens your browser. Do not add an Authorization header yourself.

Codex

codex mcp add nessie --url https://nessie.works/mcp
codex mcp login nessie

Any other MCP client

Nessie speaks streamable HTTP and the MCP authorization profile: OAuth 2.1 with PKCE (S256), dynamic client registration, refresh tokens and resource indicators. A client that supports remote servers with OAuth needs only the address. A command-line agent that cannot open a browser pairs with a short code instead; see MCP and connected tools.

What you decide when you connect

The app works in Nessie as you, and reaches only what you can reach. On the approval screen you choose:

  • What it may do. Read and change boards, read documents and write them as drafts, read Clients, work in Clients, message customers, and operate your team’s website. Messaging customers and operating the website are off unless you turn them on. Publishing a document is never a permission: the app can only ask, and you approve each one.
  • Which teams. The team you are in, and any other team of your organization you select. The app works in one team at a time and never moves anything between them.

A connection lasts 90 days. After that, connect the app again.

What it can do

  • Tickets: find projects and boards, create, edit and move tickets, comment, attach files, and manage labels, ticket types and checklists.
  • Documents: read your knowledge spaces, draft and edit documents and spreadsheets, and ask you to publish one.
  • Clients: read and work the customer inbox across email, SMS, Facebook, Instagram and website chat; keep contacts and contact lists; prepare newsletter campaigns, which a person always sends; and read contact form submissions.

Start a conversation with something like “list my Nessie projects”.

Seeing and disconnecting what you connected

Every connected app is listed in Nessie under Settings › Security › Programs signed in as you, with what it may do, which teams it reaches and when it was last used. Revoke ends it at once. An organization owner sees every connection in the organization, and can turn connecting off entirely, under Admin › Security › Programs signed in as people.

If something goes wrong

  • “Connect Nessie again.” The 90 days are up, the connection was revoked, or you signed out everywhere. Remove Nessie from the app and add it again.
  • “This connection request has expired or was already answered.” The approval screen waits ten minutes. Start connecting again from the app.
  • A tool says a permission is missing. You did not check it when you allowed the app. Revoke the connection and connect again, this time checking it.
  • “This connection can no longer reach the team…” You left that team. The connection’s other teams keep working; connect again to add it back.

For agents and tools that discover servers

Nessie publishes the standard documents an agent looks for:

  • https://nessie.works/.well-known/ai-catalog.json and https://api.nessie.works/.well-known/ai-catalog.json — the AI Catalog, naming the Server Card at https://api.nessie.works/mcp/server-card (MCP Server Cards, SEP-2127).
  • https://api.nessie.works/.well-known/oauth-protected-resource and https://api.nessie.works/.well-known/oauth-authorization-server — how to sign in (RFC 9728 and RFC 8414). An unauthenticated call to the MCP endpoint points at the first.
  • works.nessie/nessie in the official MCP Registry.
  • https://nessie.works/llms.txt — this page and the rest of the documentation, for a language model to read.