Brick Bacnet

A read-only BACnet/IP gateway that exposes building automation point databases to LLM agents via MCP, with Brick + Project Haystack semantic tagging at ingest time.

Why this exists

The research note this implementation came out of is at https://habchy.dev/research/bacnet-msi-semantic-gap. A version of the same article is also published at AutomatedBuildings.com (link will be added when the AB.com edition goes live).

Short version: vendor agentic platforms (JCI OpenBlue, Honeywell Forge, Siemens Building X, Tridium Niagara 5) keep their semantic AI layer inside their own controls portfolios. Independent MSIs running mixed-vendor 5-50 building portfolios have BACnet point databases but no clean way to expose them in semantic-tagged form to external LLM agents. This gateway is one answer to that gap.

ezhuk/bacnet-mcp does read and write at the BACnet protocol layer with no semantic normalization. This project sits beside it: it adds the Brick + Haystack tagging step at ingest and restricts the v0.1 surface to read-only for a tighter compliance footprint.

What it does (v0.1)

• Discovers BACnet/IP devices on the local broadcast domain (Who-Is, I-Am)
• Enumerates objects per device (AI, AO, AV, BI, BO, BV, MSI, MSO, MSV, Schedule, Calendar)
• Reads present-value, units, and description per object
• Tags each object with a Brick class and a Haystack tag set using rule-based mapping (rules are extensible via YAML)
• Exposes the tagged topology to any MCP host via four tools: list_devices, list_objects, get_object_value, get_tagged_topology

What it isn't (v0.1)

• Not a write path. WriteProperty is intentionally out of v0.1 for the compliance-surface reasons noted in the research article.
• Not a Niagara station integration. Fox protocol / Niagara module wrapping is a separate design.
• Not an FDD or analytics platform. The tagged topology is meant to be consumed by downstream FDD or LLM-agent workflows. This gateway is the ingest layer only.
• Not a UI. Output is MCP only. Pair it with Claude Desktop, Cursor, or any other MCP host.
• Not BACnet/SC. v0.1 is BACnet/IP only. Secure Connect is a v0.2 consideration.
• Not 223P full schema parity. v0.1 uses the simplified Brick + Haystack mapping. Full 223P entity model is a v0.2 candidate.
• Not multi-site federated. v0.1 handles one broadcast domain at a time.
• Not authenticated. v0.1 runs in a trusted local network environment.

Install

pip install brick-bacnet-mcp

Or from source:

git clone https://github.com/Yveshby27/brick-bacnet-mcp
cd brick-bacnet-mcp
pip install -e .

Python 3.11 or later required.

Quick start

Create a config file config.yaml:

bacnet:
  local_device_instance: 555001
  broadcast_address: 192.168.1.255
  polling_interval_seconds: 30
rules:
  brick: src/brick_bacnet_mcp/rules/brick_rules.yaml
  haystack: src/brick_bacnet_mcp/rules/haystack_rules.yaml
mcp:
  transport: stdio  # or "http" for a hosted MCP host
  http_port: 8080   # only if transport == http
log_level: INFO

Run the MCP server:

brick-bacnet-mcp --config config.yaml

Or wire it into Claude Desktop:

{
  "mcpServers": {
    "brick-bacnet": {
      "command": "brick-bacnet-mcp",
      "args": ["--config", "/path/to/config.yaml"]
    }
  }
}

Example interaction

With the server running and the simulator active (or a real BACnet/IP network reachable), an MCP-capable LLM can run:

User: List all the air-handling units across the building.

Agent (via MCP tool): calls get_tagged_topology(filter="brick:AHU")

Agent response: Found 3 AHUs. AHU-1 has 5 child points (discharge_air_temp, return_air_temp, supply_fan_status, mixed_air_damper_position, outside_air_temp). AHU-2 ... AHU-3 ...

See examples/ for full runnable scripts.

Checking coverage on your building

The starter rule library targets common US-style object-name conventions (OAT, DAT, ZNT, CHWS, AHU-1, etc.). Real-world mixed-vendor portfolios use wildly different naming. Before assuming the tool is broken or working, run:

brick-bacnet-mcp --coverage-report --config config.yaml

This does one discover + enumerate + tag cycle against your network and prints:

• Total objects discovered
• Brick / Haystack match percentages
• Top 20 most-common object names that no rule matched (use --top-unmatched N for a different count)
• Top 10 hottest rules

Use the unmatched list to extend the YAML rule files for your naming convention. A first-run match rate of 30-50% is normal for a portfolio that hasn't been calibrated yet; 70%+ is what you'd want before relying on the tagged topology for LLM queries.

How tagging works

The tagger applies YAML-defined rules to map BACnet object names and units to Brick classes and Haystack tag sets. The default rule set covers about 50 common HVAC, lighting, and metering object-name patterns. Users override or extend by editing src/brick_bacnet_mcp/rules/brick_rules.yaml and haystack_rules.yaml locally.

Example rule (Brick):

- pattern: '(?i)^(oat|outside_air_temp|outsideair)$'
  units: ['degF', 'degC', '°F', '°C']
  brick_class: 'Outside_Air_Temperature_Sensor'

See docs/RULES.md for the rule grammar and override conventions.

Architecture

See docs/ARCHITECTURE.md. Short version:

• discovery.py runs Who-Is broadcast, captures I-Am responses, caches device metadata
• reader.py enumerates the object list per device and polls present-value at the configured interval
• tagger.py applies Brick + Haystack rules to each enumerated object
• topology.py assembles the tagged objects into a queryable graph
• server.py exposes four MCP tools over stdio or streamable HTTP

Roadmap

v0.1 is a research instrument. The roadmap below is what the research article flagged as worth doing next IF v0.1 gets enough sustained-use signal to justify extending. None of it is committed pre-signal.

• v0.2: COV subscription support, BACnet/SC, 223P full schema parity, SkySpark / FIN Haystack-store passthrough
• v0.3+: Optional write path behind explicit opt-in, multi-site federation, authentication layer for non-local deployment

Acknowledgments

• ezhuk/bacnet-mcp for the prior-art MCP + BACnet integration that this project builds beside
• bacpypes3 for the BACnet protocol library
• Project Haystack for the Haystack tagging vocabulary and community
• Brick consortium for the Brick schema
• The named MSI voices whose published positioning this research builds on: Brian Turner (Adaptive Buildings), Marc Petock (Lynxspring), Tom Shircliff and Rob Murchison (Intelligent Buildings LLC), Jim Meacham (Altura Associates), Therese Sullivan (BuildingContext), Alper Üzmezler (BASSG)

License

MIT. See LICENSE.

Contributing

See CONTRIBUTING.md. PRs welcome for rule library extensions, documentation, examples, and test coverage. Larger changes (write path, non-BACnet protocol support, UI, FDD logic) are out of v0.1 scope. Open an issue first to discuss before submitting a PR.