# Core Concepts

## Core Concepts

| Concept | Description |
| --- | --- |
| **Origin MCP server** | A backend MCP server that exposes capabilities for a source system such as Outlook, Confluence, Salesforce, FactSet, Jira, or an internal API. |
| **MCP connector** | The administrative representation of an origin server in Unique. Admins register the URL, review tools, configure prompts, and refresh tool definitions. |
| **MCP Server Admin** | A delegated user who can configure one assigned MCP connector without tenant-wide connector admin powers. |
| **Space restriction** | A connector-level allowlist that controls which Spaces/Assistants can see, assign, and use an origin MCP server. |
| **Virtual server** | A curated MCP endpoint created from selected tools across one or more approved origins. It has its own slug, lifecycle, URL, access list, and OAuth configuration. |
| **MCP client** | An AI application that connects to MCP servers, including Unique Chat, Claude, Copilot, ChatGPT Enterprise, Cursor, Gemini, or a customer-built assistant. |
| **Hub OAuth** | The inbound authentication layer that verifies the user or client before tool calls are accepted by a virtual server. |
| **Downstream OAuth** | The per-user authentication flow between the hub and origin systems. The hub stores and applies these credentials without exposing them to the MCP client. |

## How Requests Flow

1. **Client discovers metadata.** The MCP client reads well-known OAuth and protected-resource metadata for the virtual server slug.

2. **User signs in.** The user authenticates through the hub identity provider, typically Zitadel, using OAuth with PKCE.

3. **Hub resolves policy.** The hub checks that the virtual server is published, enabled, and that the user has connect access.

4. **Tool call is routed.** The hub maps the virtual tool to its origin server, injects the correct user credentials, and relays the call.