carboncalc

carboncalc is a small local bridge to the hosted GreenCalculus MCP server, a sourced corpus of greenhouse-gas emission factors plus deterministic calculators built on top of it. You can look a factor up by its canonical key and get back not just the value but an audit envelope — who published it, the exact source reference, when it was retrieved, what licence covers it and whether the per-gas components add up — or search and resolve factors from a plain-language description when you do not yet know the key.

On top of that corpus sit the calculators: activity data into emissions, whole-life embodied carbon for materials, PCAF financed emissions for a portfolio you supply, Scope 2 electricity under both methods, freight under the GLEC framework, spend-based EEIO screening, and business travel by distance. A companion tool explains why a factor is absent from the corpus — whether no publisher issues it anywhere, it has not been sourced yet, it was declined, or the gap is coupled to another empty family.

The bridge keeps no factor data of its own. It serves the upstream server's tool list locally, exactly as captured from the live endpoint, and forwards each tool call upstream, returning the result untouched. Calculations run over inputs the caller supplies; there is no sending or payment tool in the surface.

Tools

• lookup_factor — look up one emission factor by canonical key, with its full audit envelope. Required: key.

• search_factors — find factors by free text, section, or key prefix. Optional: query, section, key_prefix, limit.

• lookup_factors — look up several factors by key in one call, each with its audit envelope. Required: keys.

• calculate_activity — emissions = activity × factor, with unit conversion to the factor basis. Required: activity, factor_key.

• calculate_embodied — whole-life embodied carbon for materials per EN 15978. Required: materials.

• calculate_pcaf — PCAF Part A financed emissions for a portfolio. Required: holdings. Optional: asset_class.

• calculate_electricity — GHG Protocol Scope 2 for purchased electricity, location-based and (when a market factor or supplier factor is given) market-based. Required: consumption, location_factor_key.

• calculate_freight — freight and logistics emissions (GLEC); the factor's denominator decides whether to send mass or teu. Required: distance, factor_key.

• calculate_spend — spend-based (EEIO) Scope 3 screening: emissions = spend × intensity factor. Required: spend, factor_key.

• calculate_business_travel — business travel emissions by the distance method. Required: distance, factor_key. Optional: passengers.

• resolve_factor — find the best factor key(s) for a plain-language description, country included in the text. Required: description.

• explain_absence — ask why a factor is not in the corpus. Optional: country, family, classification.

Related MCP server: GreenCalculus

Configuration

• GREENCALCULUS_MCP_URL (optional) — override the upstream endpoint. Defaults to https://mcp.greencalculus.com. (The override hook is this rebuild's own labelled reconstruction.)

• GREENCALCULUS_API_KEY (optional) — when set, every upstream request carries an Authorization: Bearer <key> header, for the caller's own GreenCalculus key. When it is not set, no key header is sent. (The header name is pinned by the original's registry record; the Bearer scheme and this env forwarding are labelled reconstructions — the original surface was captured keyless.)

Forwarding mechanics

On the first tool call the client opens a streamable HTTP session with the upstream: a JSON-RPC initialize request (protocolVersion 2025-03-26, clientInfo name carboncalc), then a notifications/initialized notification, then the tools/call request carrying the caller's arguments unchanged. When the upstream answers initialize with an Mcp-Session-Id header, that value rides on every later request of the session, which is reused for the life of the process. Replies may arrive as plain JSON or as server-sent events; both are read.

Successful upstream results pass through verbatim, including any isError flag the upstream sets. Failures — a JSON-RPC error, a non-2xx status, an unreadable response, or a request that cannot be completed — come back as an isError result whose text starts with carboncalc error: (this rendering is this rebuild's own labelled reconstruction).

CLI

Each tool is also a subcommand taking one JSON argument string:

npx @reneturcios/carboncalc lookup_factor '{"key":"grid.gbr.electricity.location_based"}'
npx @reneturcios/carboncalc calculate_freight '{"distance":{"value":500,"unit":"km"},"factor_key":"freight.road_hgv.tonne_km","mass":{"value":10,"unit":"tonne"}}'
npx @reneturcios/carboncalc --version

Exit codes: 0 on success, 1 on an isError result, 2 on a usage error.

MCP server

npx -y @reneturcios/carboncalc mcp

MCP client config:

{
  "mcpServers": {
    "carboncalc": {
      "command": "npx",
      "args": ["-y", "@reneturcios/carboncalc", "mcp"]
    }
  }
}

Docker

docker run -i ghcr.io/cloudcorprecords/carboncalc
docker run --rm ghcr.io/cloudcorprecords/carboncalc --version

The container's default command is mcp, so the first form is a stdio MCP server; any other arguments reach the CLI normally.

Development

npm install
npm run build
npm test
npm run dev

The test suite runs entirely against a stubbed JSON-RPC upstream — no live network calls.

License

MIT — see LICENSE.