# SHIPPING.md > A shipping skill for agents that sell and ship: your label rules, plus billable-weight, box, address and customs checks. Version 1.0. MIT. One skill file any agent can read for packing, rating and shipping parcels, with your own label spend, insurance, size and international rules written in. Read-only tools work out billable weight, size limits, the smallest box that fits, and address and customs completeness. Rates and rules come only from your own carrier accounts. 19 settings in 6 groups, numbers or fixed choices only. Presets: core, balanced, strict. Settings an agent drafted count only after the person says yes: show them to the person first, and follow them only once they agree. Use at your own risk. shipping.md is provided as is, without warranty. Information here may be inaccurate, incomplete or not current, and is not verified; figures are estimates from the numbers you send and the formulas stated. Nothing here is legal, customs, tax, hazardous-materials or professional advice. shipping.md never buys labels, quotes carrier rates or holds account credentials. Check everything yourself before you act on it. ## Skill - [SHIPPING.md](https://shipping.md/shipping.md): load into your agent's instructions or save as ~/.claude/skills/shipping/SKILL.md (sha256 40e3943c2e55841e0bba84ba7dca277685924a5d7186e94074bdaa578a3b1f06) - [SHIPPING.md with settings](https://shipping.md/shipping.md?preset=balanced): a preset plus any settings; each setting overrides the preset ## API (no key, CORS open, nothing stored) - [dim_weight](https://shipping.md/api/v1/dim_weight?length=18&width=12&height=10&unit_system=imperial&divisor=139&actual_weight=9.2&dims_rounding=nearest&weight_rounding=up_whole): Dimensional and billable weight. Works out dimensional weight (length x width x height / divisor) and billable weight (the greater of actual and dimensional weight) with the rounding you choose. The divisor is yours: common values are 139 or 166 cubic inches per pound and 5,000 or 6,000 cubic cm per kg, but check your carrier's current rule. Also returns the largest box volume that keeps dimensional weight at or under the actual weight. Arithmetic only; no rates. - [size_check](https://shipping.md/api/v1/size_check?length=40&width=20&height=18&unit_system=imperial&weight=32&max_longest=48&max_length_girth=108&max_weight=50): Check a package against your size limits. Measures a package the standard way (longest side as length; girth = 2 x the other two sides; length plus girth) and compares it, and its weight, with limits you send, usually your carrier's. Returns each check with its margin. A pass means within the numbers you sent, nothing more. - [box_fit](https://shipping.md/api/v1/box_fit): Smallest box that fits. Takes an item's size plus padding on every side and your list of boxes (inside dimensions), checks every orientation with faces parallel (or upright only), and ranks the boxes that fit by volume or by billable weight. Returns the best box, how to place the item, the empty space, and why each other box fails. It doesn't check diagonal placement, box strength or multiple items. - [address_check](https://shipping.md/api/v1/address_check?name=Sam+Lee&line1=100+Main+Street&line2=Apt+4B&city=Springfield®ion=IL&postal_code=62701&country=US&phone=%2B1+555+010+0100&from_country=US): Address completeness and format. Checks a shipping address for missing fields and format problems before you buy a label: ISO 3166-1 alpha-2 country code, region code where one is needed (US, CA, AU), postal code format for some countries, line length, characters, phone and PO box flags. Format only: it looks nothing up and can't tell whether an address exists or is deliverable. - [customs_check](https://shipping.md/api/v1/customs_check): Customs line items: completeness and flags. Checks the line items for a customs declaration: description, HS code format (6 to 10 digits, a valid chapter), quantity, unit value, ISO origin country and weight. Totals the value and weight, compares them with what you declared, and flags restricted categories by keyword and HS heading so a human can look first. It doesn't classify goods, calculate duties or check any country's rules. - [shipment_check](https://shipping.md/api/v1/shipment_check): Check a shipment plan against your rules. Compares one planned shipment (label cost, spend so far today, declared value, insurance, signature, tracking, size, weight, route, restricted items, order age, return label) with your shipping.md settings. Returns ok, ask or stop for each rule and overall. It checks the plan against your numbers; it doesn't buy, approve or quote anything. - [build_settings](https://shipping.md/api/v1/build_settings?preset=balanced): Write your settings into the skill. Turns a preset and settings into the sections written at the top of SHIPPING.md. Every setting is a number or a fixed choice; the catalog is at https://shipping.md/api/v1/settings. Returns the sections as Markdown, the settings as JSON, a link to the skill with them written in and a one-line install. Out-of-range numbers are clamped with a note. Nothing is stored. Settings an agent drafted count only after the person says yes: show them to the person first, and follow them only once they agree. - [Settings catalog](https://shipping.md/api/v1/settings): every setting with its unit, range, options and default, plus the presets - [API index](https://shipping.md/api/v1) and [OpenAPI](https://shipping.md/openapi.json) ## MCP - https://shipping.md/mcp: Streamable HTTP, stateless, no auth. Tools: dim_weight, size_check, box_fit, address_check, customs_check, shipment_check, build_settings. Prompt: shipping, with an optional preset and any setting. Resources: the skill and the settings catalog. Feedback: POST https://shipping.md/feedback with {"message": "..."} (GET it for the fields). Delivered to the site owner's feedback inbox; messages aren't stored (only short-lived, hashed counters that enforce limits). ## Terms - [Terms of use and disclaimer](https://shipping.md/terms) ## Optional - [Full text](https://shipping.md/llms-full.txt): the skill plus the tool and settings reference - [Manifest](https://shipping.md/.well-known/shipping.json)