# Other MCP clients

Canonical URL: https://support.optimonk.com/en/articles/other-mcp-clients

OAuth compatibility and the Bearer API-key fallback.

The endpoint supports Model Context Protocol over streamable HTTP. OAuth registration is limited to supported callback URLs; OAuth support alone does not make every client eligible. Other callers can use a Bearer API key if they can send an Authorization header.

**MCP endpoint**

```
https://agentic.optimonk.com/mcp
```

## What the client needs to support

- **Streamable HTTP transport.** The endpoint is stateless `POST`; there is no stdio build to install and nothing to run locally.
- **OAuth with dynamic client registration.** The client registers itself and walks the discovery chain — it needs no pre-issued credentials, but every callback URL must be allowed.

## Supported OAuth callbacks

Hosted callbacks must use HTTPS on an exact supported host: `claude.ai`, `claude.com`, `chatgpt.com`, `chat.openai.com`, `cursor.com` or `cursor.sh`. Desktop callbacks can use `cursor:`, `vscode:` or `vscode-insiders:`. Local and CLI clients can use HTTP or HTTPS loopback callbacks on `localhost`, `127.0.0.1` or `[::1]`. Callback URLs must not contain credentials or fragments.

A hosted client on another domain is rejected during registration, before consent. Use the API-key setup below for those clients.

## How discovery works

An unauthenticated call gets a `401` whose `WWW-Authenticate` header points at the protected-resource metadata, which names the authorization server. A conforming client follows that chain and, if its callback URLs are allowed, registers and opens the consent screen.

**Try the discovery chain**

```bash
curl -i -X POST https://agentic.optimonk.com/mcp \ -H 'Content-Type: application/json' \ -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'
```

## If OAuth is unsupported or registration is rejected

Create an API key under `Settings → API & Connected apps` and send it as a Bearer token. Same endpoint, same tools — see [Authentication & access](/en/articles/authentication-and-access).

## What you should see

For OAuth, complete your client’s authentication flow, then approve the requested OptiMonk permissions. See [Authentication & access](/en/articles/authentication-and-access) for consent-screen details and connection management.

## Check it worked

Ask your agent to call `whoami`. It answers with the account it is acting as and the permissions it holds, which is also the first thing to check if a later call says something is missing.

## If it does not connect

- **Nothing happens after adding the URL.** Complete your client’s authentication step first. If the consent tab is blocked, allow pop-ups for this site and retry.
- **You were asked for a key or token.** OAuth connections do not require an API key. If your client does not support OAuth or its callback is not allowed, use a Bearer API key instead — see [Authentication & access](/en/articles/authentication-and-access).
- **Connected, but calls fail.** Call `whoami` first: a credential on the wrong account fails exactly like a missing object.