> ## Documentation Index
> Fetch the complete documentation index at: https://docs.paperzilla.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# How do clients discover the Paperzilla MCP URL and tools?

> How MCP clients find the Paperzilla server URL, discover available tools, and how this differs from OpenAPI.

export const AiAgents = ({path}) => <Tip>
    <b>AI agents</b>: This page is available as <a href={path + '.md'}>markdown</a>. See also the <a href="/llms.txt">docs index</a> and <a href="/llms-full.txt">full docs</a>.
  </Tip>;

<AiAgents path="/answers/how-do-clients-discover-paperzilla-mcp" />

The MCP server URL is discovered out-of-band.

For Paperzilla, that usually means your client or user starts with the documented endpoint from the docs, app setup instructions, or docs indexed via `llms.txt`:

`https://paperzilla.ai/api/mcp`

This URL does **not** come from OpenAPI.

## What happens after the client knows the URL

Once the client is pointed at the MCP endpoint and has a valid MCP API key, it can discover the callable surface from MCP itself.

In practice, the client initializes the MCP connection first, then calls:

1. `tools/list`
2. Optionally `prompts/list`

`tools/list` returns the available tool names plus input schemas, so the client can see what calls exist and what arguments they take.

That includes feed browsing and search tools such as:

* `feed_get`
* `feed_search`
* `paper_get`
* `paper_markdown`

That means MCP is self-describing after connection.

## Does MCP have its own endpoints?

Externally, no per-tool endpoints are required.

Paperzilla exposes one MCP endpoint at `/api/mcp`, and tool calls happen over that protocol connection.

Internally, those tools are backed by Paperzilla's own app logic and data access. A tool may read directly from internal services or data stores instead of calling the public REST API.

## How this relates to OpenAPI

OpenAPI documents a REST API.

MCP tool discovery works differently:

* OpenAPI tells a REST client which HTTP routes exist
* MCP tells an MCP client which tools exist through `tools/list`

So if you are building an MCP client for Paperzilla, you usually need:

* The MCP server URL
* An MCP API key
* Standard MCP calls like `initialize` and `tools/list`

Use OpenAPI only for Paperzilla's normal REST endpoints, not for MCP tool discovery.

See also:

* [Use Paperzilla with MCP](/guides/mcp)
* [MCP endpoint (developer appendix)](/api-reference/mcp)