Configuration

Configuration Resolution

Configuration resolution is the process by which user-supplied values are matched to the config slots declared in the manifest.

Config Value Resolution Order

When resolving a config variable, the installer MUST use the following precedence order (highest to lowest):

1. User-supplied value — provided interactively during install or pre-configured in host settings.
2. Config default — the default value declared in the manifest config slot.
3. Error — if the slot is required and no value is found, the installer MUST report an error.

If a slot is not required and no value is available from steps 1 or 2, the variable is treated as unset.

Storage

Config values are stored in the host’s settings mechanism, namespaced under the package name:

{
  "packages": {
    "api-testing": {
      "API_BASE_URL": "https://api.example.com",
      "API_KEY": "sk-...",
      "ENVIRONMENT": "staging"
    }
  }
}

• Values of type secret MUST be masked in all log output and MUST NOT appear in lockfiles.
• Installers SHOULD store secrets using the host’s secure storage mechanism when available.

Variable Substitution

Template variables in .mcp.json and .lsp.json files use the syntax ${config.VARIABLE_NAME}. The substitution rules defined in MCP Servers > Variable Substitution apply. Substitution occurs at install time when templates are rendered to their final form.