Configuration

Three environment variables; only the first is required.

Variable	Required	Description
RUSTPAD_URL	yes	Base URL of the instance, e.g. https://rustpad.example.net
RUSTPAD_READ_ONLY	no	true registers only the read tools
RUSTPAD_INSECURE_TLS	no	true accepts self-signed certificates (scoped to this connection only)

One URL for everything

RUSTPAD_URL serves three purposes: the HTTP API (/api/text, /api/stats), the collaboration WebSocket (http/https is mapped to ws/wss), and the share links the tools return (<RUSTPAD_URL>/#<pad-id>). If your instance sits behind a reverse proxy, that proxy must forward WebSocket upgrades on /api/socket/….

The URL is validated on start: only http:/https:, no embedded credentials, no query string or fragment. A plain-http URL to a non-loopback host starts with a warning — everything, including full pad content, would travel unencrypted. A malformed URL exits instead of limping along.

Boolean semantics

The two flags compare against exactly the string true. True, 1 or yes count as false — deliberately strict, and the reason the server prints a banner on start when read-only or insecure-TLS mode is actually active.

Ephemerality

Rustpad keeps documents in memory; they are lost when the server restarts and after 24 hours without an open connection. If you want pads to survive, run the Rustpad instance itself with SQLITE_URI (see the Rustpad README) — nothing changes on the rustpad-mcp side.

Limits worth knowing

• Documents are capped at 256 KiB by Rustpad itself; the server checks before sending and refuses edits that would exceed it.
• Tool results are budgeted to ~200 000 characters; a larger pad is truncated with an explicit notice rather than silently cut.
• Every network wait has a wall-clock timeout (15–20 s); a hostile or hung upstream costs a failed tool call, never a hung server.