takeoffmetric-mcp

takeoffmetric-mcp

A Model Context Protocol server (stdio) that runs the construction calculators of TakeoffMetric (https://takeoffmetric.com/) from an MCP client. It ships 15 calculators, a tool that lists them, and a search over a table of estimating constants in which every row names its published source.

The calculators are not re-implemented here. The site's TypeScript engine is bundled unchanged into vendor/engine.mjs, and the test suite checks that each tool returns what the engine source computes.

Install

Requires Node.js 20 or later.

npx -y takeoffmetric-mcp

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "takeoffmetric": {
      "command": "npx",
      "args": ["-y", "takeoffmetric-mcp"]
    }
  }
}

Claude Code:

claude mcp add takeoffmetric -- npx -y takeoffmetric-mcp

Tools

Tool	What it returns
calc_concrete_slab	Concrete volume, order quantity, bags, truck loads and weight for a slab, with extra sections and an optional thickened edge.
calc_concrete_cost	Concrete cost from your own delivered price, with short-load fee, delivery, and bags compared with ready-mix.
calc_rebar	Bar count each way, lap splices, stock bars, weight, intersections and supports for a slab grid or a continuous footing.
calc_gravel	Cubic yards, short tons and metric tonnes of gravel, stone or rock, with the compaction conversion and a truck count.
calc_fill_dirt	Cubic yards, tons and truck loads of fill dirt, loose or in place.
calc_sand	Cubic yards, short tons and a bag count for sand, by moisture condition.
calc_topsoil	Cubic yards, bags, weight and coverage of topsoil for a lawn, a top-dressing pass, a garden bed or a raised box.
calc_cubic_yard	Cubic yards, cubic feet and cubic meters over several areas, the area a volume covers, swell, bags and truck trips.
calc_asphalt	Short tons and metric tonnes of hot mix by course and by area, with the spread rate.
calc_board_foot	Board feet, lineal feet, pieces and cost for a lumber order of several sizes.
calc_roofing	Squares, shingle bundles, underlayment rolls, ridge cap and starter from the plan footprint and the pitch.
calc_roof_pitch	Rise in 12, angle, grade and slope factor from any one of them, plus ridge height and common rafter length from a span.
calc_fence	Posts, rails, pickets, gates and post-hole concrete for a fence line.
calc_duct	Round and rectangular duct size from airflow and a friction rate or velocity limit, what a duct carries, and a reducing trunk.
calc_paver_base	Crushed stone base, bedding sand and excavation depth under a paver patio, driveway or street.

Two more tools complete the server:

• list_calculators: tool name, title, page URL, one-line description and input keys of each calculator.
• search_constants: rows of the constants table matched by a substring (query) and/or a category, 50 rows at most per call.

Inputs

Each calculator's input schema is generated at start-up from the engine's own input list, so keys, bounds, options and defaults are the ones of the matching form on the site.

• Every input is optional. A key you leave out takes the engine default, as an untouched form field does, with one exception: a value whose publisher does not allow republication is never a default (see below).
• system is "imperial" (default) or "metric". It sets the unit the numbers are typed in and the defaults.
• A length is a number in the unit named in its description, or a string that carries its unit, such as "20 ft 6 in".
• An unknown key or an out-of-range value returns isError: true with one message per field. Nothing is computed from a clamped value.

Values you type (0.2.0)

Some site defaults are publisher figures that this package does not republish (dataset rows with values_withheld). They are inputs with no default, read off your own product, plan or supplier. Without them a tool returns what it can compute (geometry, volumes) and a needed list of the missing inputs.

Tool	Inputs with no default
calc_concrete_slab, calc_concrete_cost, calc_fence	bagYield (cu ft or L per bag; the bag-weight select is gone)
calc_paver_base	baseDensity, beddingDensity
calc_gravel, calc_sand	density
calc_asphalt	plantWeight (the two published presets are gone)
calc_rebar	stockLength (the stock-length select is gone)
calc_roofing	bundlesPerSquare, rollSquares, ridgeLfPerBundle, starterLfPerBundle
calc_duct	eps (roughness; without it no size)

Output

A JSON text block: calculator, url, system, engine_version, revised, inputs_used, primary, secondary, takeoff, warnings, assumptions, and needed when an input above is missing. inputs_used is the engine's normalized input (lengths in metres). assumptions lists what the result rests on, and warnings carries the cautions the page would show.

Worked example

Request (tools/call, tool calc_concrete_slab). bagYield is the yield printed on the bag you buy (0.5 cu ft here, a synthetic figure): without it the answer has no bag count and lists bagYield in needed.

{"length":24,"width":16,"thickness":"5 in","price":165,"bagYield":0.5}

Response, copied from a run of this server (0.2.0):

{
  "calculator": "calc_concrete_slab",
  "url": "https://takeoffmetric.com/concrete/concrete-calculator/",
  "system": "imperial",
  "engine_version": "1.3.0",
  "revised": "2026-10-01",
  "inputs_used": {"system":"imperial","sections":[{"length":7.315200000000001,"width":4.8768},{"length":0,"width":0},{"length":0,"width":0}],"thickness":0.127,"wastePct":10,"pricePerCuYd":165,"thickenedEdge":false,"edgeDepth":0.30479999999999996,"edgeWidth":0.30479999999999996,"gravelDepth":0.1016,"unitWeight":150,"truckCuYd":10,"minLoadCuYd":null,"shortLoadFee":null},
  "primary": {"value":5.93,"unit":"cuyd","label":"Concrete volume","precision":2},
  "secondary": [
    {"value":6.75,"unit":"cuyd","label":"Order quantity","precision":2},
    {"value":160,"unit":"cuft","label":"Concrete volume","precision":1},
    {"value":384,"unit":"sqft","label":"Slab area","precision":0},
    {"value":26400,"unit":"lb","label":"Concrete weight","precision":0},
    {"value":1,"unit":"load","label":"Truck loads","precision":0},
    {"value":10,"unit":"ft","label":"Control-joint spacing","display":"10'-0″ to 15'-0″"},
    {"value":1113.75,"unit":"usd","label":"Estimated concrete cost","precision":2},
    {"value":352,"unit":"bag","label":"Bags","precision":0}
  ],
  "takeoff": [
    {"key":"readymix","item":"Ready-mix concrete","qty":5.93,"unit":"cuyd","waste":10,"order":6.75,"orderUnit":"cuyd","note":"Rounded up to the nearest 0.25 cu yd."},
    {"key":"trucks","item":"Ready-mix truck loads","qty":6.52,"unit":"cuyd","order":1,"orderUnit":"load","note":"10 cu yd per load (your assumption)."},
    {"key":"gravel","item":"Compacted base, 4″","qty":4.74,"unit":"cuyd","order":6.5,"orderUnit":"cuyd","note":"Loose volume ordered = compacted volume x 1.31 (3,570 / 2,730 lb/cu yd, FHWA Exhibit 5.1 A, gravel dry, average gradation; 1.17 uniformly graded, 1.49 well graded). For estimating purposes, ±33%: a highway embankment, not a plate-compacted base."},
    {"key":"cost","item":"Concrete cost at your price","qty":6.75,"unit":"cuyd","order":1113.75,"orderUnit":"usd","note":"6.75 cu yd x $165.00 / cu yd."}
  ],
  "warnings": [],
  "assumptions": [
    "Volume = length x width x thickness; 1 cubic yard = 27 cubic feet.",
    "Waste allowance 10% applied to the net volume.",
    "Ready-mix rounded up to 0.25 cu yd; truck capacity 10 cu yd (editable).",
    "Unit weight 150 lb/cu ft (editable; normal-weight concrete runs about 140-155).",
    "Contraction joints at 24-36 times the slab thickness, capped at 15 ft (NRMCA CIP 6).",
    "Thickness, reinforcement and base depth come from your drawings or local code.",
    "Bags = volume / the bag yield you entered (0.5 cu ft a bag), rounded up."
  ]
}

How the numbers are sourced

• Formulas, constants and rounding rules come from the engine bundle. vendor/ENGINE_COMMIT.txt records the commit it was built from, and every response carries the calculator's engine_version and revised date.
• Each tool computes with the same engine as its page on the site. calc_gravel, for instance, runs the engine behind https://takeoffmetric.com/earthwork/gravel-calculator/.
• search_constants reads vendor/constants.csv (dataset 1.2.0, 148 rows). Each row gives the value, its unit, the SI value, the condition it applies to, and the publisher, title and URL of the document it was read from. 55 rows carry no value because their publishers do not allow republication: they return value: null, values_withheld: true, the publisher's domains in withheld_hosts, and the URL where the value can be read.
• The site's methodology (tested formulas, assumptions shown on the page, sources as documents, versioned sheets) is at https://takeoffmetric.com/methodology/.

Limits

• Results are estimates. Confirm quantities with your plans, your supplier and your local code before ordering or building.
• This release covers 15 calculators. Calculators that apply building-code provisions, or that rely on third-party tables the site links to without reproducing them, are not part of it.
• Responses carry numbers and notes only: no drawing and no CSV export.
• unit fields use the engine's unit codes. Several results that are not plain counts are coded ea; read label and display for their meaning.
• Prices are whatever you type in. The server holds no price data and makes no network request.
• Transport is stdio only.

Development

npm install
npm test

The tests run with this repository alone. npm run sync-engine and npm run make-fixtures are maintainer scripts: they rebuild vendor/ and test/fixtures.json from the site's source repository, which users of the package never need.

License

Server code: MIT. Calculation engine (vendor/engine.mjs): copyright TakeoffMetric, distributed with this package to run as part of it, not licensed for modification or separate redistribution. Both are set out in LICENSE. Constants table: CC BY 4.0 for the compilation; federal values are public domain; any other value stays under its publisher's terms. See DATA_LICENSE.md.