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MCP Overview

4 min readLast updated Oct 19, 2026

Connect a remote MCP client using OAuth and Client ID Metadata Documents (CIMD).

Efimis tools describe their own purpose and inputs. The server tailors tool availability to the user’s permissions and descriptions to the firm’s region. This guide explains connection, sign-in and verification.

Efimis currently supports Claude, Codex and ChatGPT as CIMD clients. If you want to use another client or build your own integration, contact connections@efimis.com before connecting so we can review compatibility and support requirements.

At a glance

Section titled “At a glance”
Item Value
Server Efimis MCP
MCP URL UK: https://api.uk.efimis.com/mcp; AU: https://api.au.efimis.com/mcp
Transport Streamable HTTP
Interactive sign-in OAuth authorization code with PKCE
Client identification CIMD, where advertised and supported by the client
Request authentication OAuth access token in the Authorization header
User Determined by Efimis sign-in
Firm Resolved through your Efimis account
Supported CIMD clients Claude, Codex and ChatGPT

Your client handles OAuth sign-in and client identification. See Authentication for sign-in help and further reading on MCP, CIMD and PKCE.

What you need from Efimis

Section titled “What you need from Efimis”

You need:

  • The region that hosts your firm: UK or AU.
  • An Efimis account with access to the intended firm and tools.
  • Any client approval or firm-administrator approval required.
  • Access to one of the three supported CIMD clients.

Choose the regional MCP URL above. The regional hosts are listed in the Efimis REST API guide. MCP uses the /mcp endpoint on that host. Enter that URL in your client and complete interactive sign-in.

Claude, Codex and ChatGPT manage their own client identification. You do not need to provide a client ID, client secret, tenant ID, user ID or manually obtained bearer token, or publish a metadata document.

Connect from an MCP client

Section titled “Connect from an MCP client”
  1. Add a remote MCP server named Efimis.
  2. Enter your regional MCP URL and select Streamable HTTP if prompted.
  3. Start the connection and follow the client’s sign-in prompt.
  4. Sign in with your Efimis account.
  5. Complete the authorization prompts.
  6. Allow the client to finish connecting, then verify the available tools.

Claude

Section titled “Claude”
  1. Open Customize > Connectors and choose Add custom connector. In a managed workspace, an administrator may need to add it through Organization settings > Connectors first.
  2. Name it Efimis and enter your regional MCP URL.
  3. Review the detected authentication settings and choose Sign in now.
  4. Under OAuth client, select Use Claude’s published identity for CIMD.
  5. Finish adding the connector. Select Connect if prompted and sign in to Efimis.
  6. Enable Efimis for the conversation through the connector picker.

See Claude’s remote connector guide.

Codex

Section titled “Codex”

For example, add the UK endpoint using the Codex CLI, then start CIMD sign-in:

Terminal window
codex mcp add efimis --url https://api.uk.efimis.com/mcp
codex mcp login efimis --oauth-client-registration cimd

For AU, use https://api.au.efimis.com/mcp instead. Complete the browser sign-in. Run codex mcp list to check the configuration; in the Codex CLI, use /mcp to inspect the connection and tools. Use a current version that supports CIMD.

See OpenAI’s Codex MCP guide.

ChatGPT

Section titled “ChatGPT”
  1. In ChatGPT on the web, open Plugins.
  2. Select the plus button, then Add custom MCP server.
  3. Name it Efimis and enter your regional MCP URL under Connection.
  4. Select OAuth authentication and choose CIMD as the client registration method. Leave static client credentials empty.
  5. Review the prompts and create the plugin, then install it for use in conversations.
  6. Complete Efimis sign-in when prompted.
  7. In a conversation, type @ and select Efimis to use its tools.

Workspace permissions may require an administrator to add or approve the connection. See OpenAI’s custom MCP server guide.

Verify the account and tools

Section titled “Verify the account and tools”

Check the signed-in account. After initialization, the client discovers tools through tools/list; confirm they match your access. Where available, use a read-only profile or firm-context tool to verify your firm.

A successful tool listing establishes connectivity, but does not by itself prove that the selected user and firm are correct. Do not use a write action as a connection test.

Learn how authentication works and how to build an agent around the available tools.