bacnet-mcp

A Model Context Protocol server for BACnet sites, read-only unless a profile offers writes, in the Rusty BACnet workspace. An AI agent host (Claude Code, Codex and others) launches it as bacnet mcp serve --stdio (the bacnet-cli feature mcp) and calls its tools to discover devices, describe them, find, list and read their objects, read and summarise trend logs, event logs and audit logs, list alarms, map networks, routers and BBMD tables, decode frames, follow points as they change, and, when a profile allows it, write and revert values.

• Built on the official rmcp SDK; targets the 2026-07-28 revision of MCP and still answers the older initialize handshake.
• Every request goes through the bacnet-ops engine and its limits: one request at a time per device, a global rate, a rate per network and a token bucket per principal. Each result reports what it cost.
• Device-supplied text comes back in an untrusted envelope: cleaned of control and bidirectional characters, defanged and capped.
• Results are paged with cursors signed by a per-process key.
• Passive mode builds no client and sends nothing.
• Resources for devices, points, properties, alarms, the session and the write ledger, with subscriptions/listen (2026-07-28), or resources/subscribe from hosts on older revisions, on a shared watch hub: one COV subscription per point however many listeners, polling when a device refuses COV, 32 points per principal and 256 per process. bacnet_watch gives hosts without subscriptions the same through a tool.
• Writes are off by default. A policy that offers them lists bacnet_write and bacnet_revert, which go through the TUI's preview tiers, ledger and audit log (bacnet-ops::safety): the client's confirmation may approve T1 writes only, a plan grant the writes it names, and the confirmation state is sealed for its caller, single use and short-lived.

Experimental in 0.15; the API (McpServer, Policy) may change in any release before 1.0. The design is docs/design/mcp.md.