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

# MCP servers

> Connect your own MCP servers to Helix. Their tools reach the model directly.

Helix speaks the Model Context Protocol (MCP). It ships no MCP server of its own: the servers you
configure are the ones it uses, and their tools reach the model directly, next to Helix's own tools.

## Add a server

List your servers in an `mcp.json` file, in the `mcpServers` shape other MCP clients use:

| File | Applies to |
| - | - |
| `~/.mutagent/agent/mcp.json` | Every Helix session on your machine. |
| `.pi/mcp.json` in your project | Sessions in that project, once you trust it. |

```json mcp.json theme={null}
{
  "mcpServers": {
    "filesystem": { "command": "npx", "args": ["-y", "@modelcontextprotocol/server-filesystem", "."] },
    "docs": { "url": "https://example.com/mcp", "headers": { "Authorization": "Bearer ${DOCS_TOKEN}" } }
  }
}
```

A local server runs from `command` and `args`; a remote one is reached at `url`. The next Helix
session loads them.

## How the model sees the tools

Each tool is offered to the model as `mcp__<server>__<tool>`, for example
`mcp__docs__search`. The model calls it like any other tool.

<Note>
  Leave a server's `exposure` field out, or set it to `"direct"`. A server set to `"codemode"` or
  `"deferred"` has no tools Helix can call, and Helix warns about it.
</Note>

## Where MCP tools are available

| | MCP tools |
| - | - |
| `helix` and `helix agent` | Offered to the model directly. |
| `helix --prime` | Called from code: a cell can search your MCP tools, read a tool's parameters and call it. See [Prime](/helix/modes#helix-prime-the-code-first-mode). |
| Sub-agents | Not available. A sub-agent works with Helix's own tools. |

<Card title="Project context" icon="arrow-right" href="/helix/features/project-context">
  The other thing every session loads from your project: `AGENTS.md` / `CLAUDE.md`.
</Card>


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