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Configuration

acf-mcp is configured via environment variables. No secret is ever required: the server holds nothing sensitive. This page lists each variable, its purpose, its default, and the two available transports (stdio and HTTP).

iNote
No server-side secret. acf-mcp stores no API key, no token, no credentials. The variables below tune the locale, the transport and the doctrine archive URL — nothing authenticating.

Environment variables

ACF_LOCALEstringdefault: "en"
Server reply locale. Supported values: en, fr. Affects the language of explanations inside REASON tool outputs and the content returned for bilingual resources.
ACF_DOCTRINE_ARCHIVE_URLstring
Absolute URL of the signed doctrine archive that the signed footer must reference. Defaults to the official version hosted on acfstandard.io. Override this variable to point at your internal mirror or an air-gapped environment.
ACF_HTTP_PORTintegerdefault: 3000
Listen port when running with HTTP transport. Ignored in stdio mode (the default). Enabled by passing --transport http on the command line.

Available transports

Two transports are shipped. stdio is the default, intended for a single user on their own machine. HTTP exists for multi-user deployments behind your own gateway.

Default transport. The client launches the binary on demand via npx and talks JSON-RPC over stdin/stdout. No port, no network setup.

client-config.jsonjson
{
  "mcpServers": {
    "acf": {
      "command": "npx",
      "args": ["-y", "acf-mcp"],
      "env": {
        "ACF_LOCALE": "fr"
      }
    }
  }
}

Self-hosted doctrine archive

For an air-gapped deployment or one controlled by an internal source of truth, mirror the signed archive and point ACF_DOCTRINE_ARCHIVE_URL at your URL. The signed footer will reflect that mirror, keeping the auditor trace consistent with your infrastructure.

bash
# Point the signed-footer at your self-hosted doctrine mirror
ACF_DOCTRINE_ARCHIVE_URL=https://acf.internal.example.com/doctrine/v1.0/archive.json \
  npx -y acf-mcp
!Warning
If you change the archive URL, you remain responsible for the availability of the signed file for your auditors. The Ed25519 signature remains valid as long as you serve the doctrine unmodified.

CLI flags

--transportenumdefault: "stdio"
Transport to use. Values: stdio (default), http.
--versionflag
Prints the server version, the loaded doctrine_version and the Ed25519 public key, then exits.
--helpflag
Prints help and exits.

See also