Servers are references to MCP (Model Context Protocol) servers declared in a facet’s manifest. Unlike skills, agents, and commands, servers are linked rather than embedded — the facet manifest references them, but server code is never included in the facet archive.
Two execution modes
Facets support two ways to reference MCP servers:
| Mode | Manifest value | Resolution |
|---|
| Source-mode | String (floor version): "1.0.0" | Published to the facets registry as a separate server artifact. The version is a floor constraint — the CLI may install a newer compatible version. |
| Ref-mode | Object: { "image": "ghcr.io/..." } | OCI container image in an external registry (GHCR, Docker Hub, ECR). Pinned by tag and resolved digest. |
Source-mode example
{
"servers": {
"sqlite": "1.0.0"
}
}
Ref-mode example
{
"servers": {
"sqlite": { "image": "ghcr.io/acme/sqlite-mcp:v1.2" }
}
}
Server manifest
Source-mode servers have their own manifest (server.json) with these fields:
| Field | Type | Required | Description |
|---|
name | string | Yes | Server name |
version | string | Yes | Semver version |
runtime | string | Yes | Runtime to execute the server (day-one: bun only) |
entry | string | Yes | Entry point file |
description | string | No | Human-readable description |
author | string | No | Author name or identifier |
Execution contract
- The CLI manages the server process lifecycle: start, stop, restart.
- Communication uses stdio (source-mode) or stdio/HTTP (ref-mode).
- Servers are terminal — they must not declare dependencies on other servers. Resolution is always one level deep.
Current status
Server support is in development. A facet that declares servers: emits a warning during install — the server names are listed but not materialized. Server materialization is planned for open beta. The day-one runtime is Bun only.
Further reading
