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Custom MCP lets Tess act as an MCP client. You register a remote server (Attio, Gleap, Volt, Supabase, an internal tool, or any Streamable HTTP MCP endpoint), Tess discovers its tools, and those tools become available in chat and agents — alongside native Connectors. This is the opposite direction of the Tess MCP Server, which exposes Tess to Claude, Cursor, and other MCP clients.

Tess MCP Server

Use Tess agents, files, and memories from Claude, Cursor, Codex, or any MCP client. Endpoint: https://mcp.tess.im.

Custom MCP

Bring an external MCP server into Tess. Your chats and agents call that server’s tools with your credentials.
Custom MCP is available when the workspace feature is enabled. Native Apps (Gmail, Slack, Notion, and the rest of the catalog) stay under Connectors — use Custom MCP for servers that are not in that catalog.

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Before you start

You need:
  • A remote MCP endpoint that speaks Streamable HTTP (not a local npx/stdio process).
  • Permission to create personal MCP servers (or governance permission, if you will share the server with the workspace).
  • Credentials the server expects: OAuth (interactive sign-in) or a static token (Bearer, API key, or custom headers).
Keep personal accounts personal. A WhatsApp, email, or CRM MCP tied to your identity should stay a personal server. Sharing it with the workspace lets other members opt in and call those tools. See Sharing and permissions.

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Add a Custom MCP server

1

Open Connectors

In chat, click + → Connectors → Add connectors, then open the Custom MCP lane. You can also manage servers from Settings → MCP Plugins.
2

Enter the endpoint

Give the server a name and paste the remote URL (for example https://mcp.attio.com/mcp or https://mcp.voltchat.com/mcp). Tess only accepts allowed remote HTTP(S) endpoints.
3

Choose how you authenticate

  • OAuth — Tess discovers the server’s auth metadata and opens a popup so you authorize your account. Allow pop-ups to finish the flow.
  • Bearer / API key / custom header — paste the token Tess should send on every call to that server.
4

Save, then connect

After saving an OAuth server, click Connect and complete the provider login. Tess then syncs the tool list. Do not enable the server in chat until the connection succeeds — an OAuth server with no connected token cannot run.
5

Enable the tools you want

Each tool can be turned on or off for you. Disabling a tool never changes another member’s selection. In chat, select the MCP in Connectors like any other app so the agent is allowed to call it.
New servers are personal by default. Sharing with the workspace is a separate, explicit action and requires governance permission.

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Authentication models

Prefer OAuth when the provider supports it (Attio, Meta Ads, and many hosted MCPs). Each member who uses a shared OAuth MCP must click Connect and sign in with their own account. Tess never reuses someone else’s OAuth token.

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Use it in chat and agents

Once the server is connected and enabled for you:
  • Chat — select it under Connectors (same control as Gmail or Slack). If it is not selected, Tess will not inject its tools for that turn.
  • Agent Studio — add it to the agent’s connector policy, or leave User decision on so each end user chooses at run time.
  • Tool chips — turn individual capabilities on or off without deleting the server.
A shared MCP that you have not opted into does not appear in your chat. Opt in from MCP Plugins or the Connectors modal first. Details: Sharing and permissions.

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What Tess does with the server

  1. Discovers tools (and resources, when the server exposes them) over MCP.
  2. Converts them into the same tool format used by native Tess tools.
  3. Injects only the tools you enabled, and only if the server is connectable (valid static credential, or a connected OAuth token).
  4. Calls the remote server with your credential. Executions follow workspace credit and permission rules.
If a server has no usable credential for you, Tess hides it from tool discovery instead of calling it unauthenticated.

Sharing and permissions

Personal vs shared servers, opt-in, and who can create, share, or delete.

Best practices

OAuth discovery, troubleshooting, and how to keep personal tools from leaking across the workspace.