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

# MCP Servers

> Portable server declarations in a facet

A facet can declare [MCP servers](/specification/manifest#mcp-server-declarations) alongside its skills, commands, and agents. A declaration is portable connection information, not a package reference: there is no server registry, version range, or image.

A server is an asset, but not a [text asset](/specification/manifest#text-assets). It is versioned, integrity-checked, and materialized on install like the rest of a facet, but it lands in a different place: a keyed entry inside each connected tool's configuration rather than a file your project owns. A facet may declare servers and nothing else.

## Example

```json facet.json theme={"theme":{"light":"github-light","dark":"github-dark"}}
{
  "servers": {
    "filesystem": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-filesystem", "."]
    },
    "docs": { "type": "http", "url": "https://mcp.example.com/docs" }
  }
}
```

A `stdio` server names a command and its ordered arguments. An `http` server names an absolute URL. Declaration objects are closed: an unrecognized member is rejected rather than ignored.

## Approval

Configuring a server lets your coding tool run a command or open a connection, so a new or changed declaration needs your approval before anything is written. Interactive runs show one screen with Decline selected by default. Non-interactive runs need [`--accept-mcp`](/cli/install#mcp-servers).

Approval is machine-local. It is never recorded in `facets.json` or `facets.lock`, so a teammate who clones your project approves on their own machine.

## Naming and refusal

Servers are aliased and omitted per project exactly like text assets, under the `servers` group in [`facets.json`](/specification/project-manifest). They occupy their own identity space, so a server named `deploy` never collides with a skill, command, or agent named `deploy`.

Two facets declaring the same server identically agree and produce one entry. Two facets declaring different servers at one name is a collision you resolve like any other.

## What Facets does not do

Facets writes configuration. It never installs, launches, connects to, health-checks, or authenticates to a declared server, and stores no credentials. Sign-in happens in your coding tool afterwards.

<Warning>
  `env` values are literal strings that ship inside the published archive. Never put a secret in one.
</Warning>

## Further reading

* [MCP server declarations](/specification/manifest#mcp-server-declarations)
* [`facet install`](/cli/install#mcp-servers)
* [Adapters](/docs/learn/adapters)