---
title: "Generic / custom client"
description: "Connect any MCP-compatible client or your own agent to Unitpost."
url: https://www.unitpost.com/guides/mcp/custom
section: MCP
updated: 2026-08-28
---
# Generic / custom client

## Connection settings

- **Server URL**: https://mcp.unitpost.com/mcp
- **Transport**: Streamable HTTP
- **Auth (recommended)**: OAuth 2.1 — add the URL, approve in the browser (scopes match API capabilities; tokens refresh automatically)
- **Auth (legacy)**: Authorization: Bearer pk_live_YOUR_KEY (workspace API key from Settings → API keys; for clients that can only paste a key)
- **Tools**: one per API operation (email_send, email_campaigns_send, …)

## Generic / custom client

> Connect any MCP-compatible client or your own agent to Unitpost.

Any streamable-HTTP MCP client that speaks MCP OAuth connects with just the URL. Anything else uses a Bearer API key.

### 1. Connect with OAuth (recommended)

Point the client at the server URL below. A spec-compliant client discovers OAuth itself: it reads the `WWW-Authenticate: Bearer resource_metadata="…"` challenge on the first 401, fetches `/.well-known/oauth-protected-resource`, runs the PKCE code flow against the advertised authorization server, and retries with the token. No key to copy. Your client opens Unitpost in the browser — pick a workspace, approve the scopes, and you're connected. Tokens refresh automatically.

- Server URL: https://mcp.unitpost.com/mcp
- Transport: Streamable HTTP
- Auth (recommended): OAuth 2.1 — add the URL, approve in the browser
- Auth (legacy): Authorization: Bearer pk_live_YOUR_KEY
- Tools: one per API operation (email_send, email_campaigns_send, …)

### 2. Discover tools

The server advertises one tool per API operation (`email_send`, `email_campaigns_send`, `email_domains_verify`, …). A write's `body` maps to the API request body. Every tool declares `securitySchemes: [{ type: "oauth2", scopes: […] }]` so linking-aware clients (ChatGPT) show the Connect UI.

### 3. Verify

Call a read tool (e.g. list domains). An unauthenticated call answers 401 with a `WWW-Authenticate: Bearer resource_metadata="…"` challenge (start OAuth there). With a key, a 401 Invalid API key usually means a missing `Bearer ` prefix or a mistyped key — recreate the key and retry.

> Don't see it? Fully quit and reopen the client — closing the window is often not enough — then check again.

Every MCP call uses the same pipeline as the REST API (scopes, rate limits, suppression, tracking, webhooks). Full tool list: /api/v1/openapi.json.

## Related

- [Headless / API key](https://www.unitpost.com/guides/mcp/headless): No browser on this machine? CI, SSH, containers, or paste-a-key-only clients — use a key.
- [Cursor](https://www.unitpost.com/guides/mcp/cursor): Connect Cursor to Unitpost with OAuth — approve in the browser, or a key block.
- [Claude Code](https://www.unitpost.com/guides/mcp/claude-code): Connect Claude Code to Unitpost with OAuth — add the URL, authenticate from /mcp, approve in the browser.