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17×7

17x7 API & MCP server

The math behind every 17x7 calculator, plus time zone and cron utilities — as a keyless JSON API and a remote MCP server your AI agent can call. Free, no sign-up.

  • MCP: Streamable HTTP, no auth
  • JSON API: GET or POST
  • Calculator results include their steps

MCP server

Endpoint: https://api.17x7.com/mcp — stateless Streamable HTTP, no authentication, works with clients speaking MCP 2025-06-18 or later. It exposes six read-only tools:

ToolWhat it does
convert_timeConvert a moment between IANA time zones with DST handling (flags ambiguous and skipped wall times).
explain_cronPlain-English description of a cron expression plus its next run times in any time zone.
etsy_feesEtsy fees and profit for one order (2026 rates, 12 seller countries, Offsite Ads, Share & Save).
amazon_fba_feesAmazon US FBA size tier, fulfillment, referral and storage fees, margin and ROI (2026 rate card).
roof_pitchRoof pitch, degrees, slope, multiplier, rafter length, roof area, squares and shingle bundles.
deck_materialsDeck boards (cut-aware), joists, hangers, screws or clips, IRC span check and cost.

Browser-only, with no API or MCP tool: JSON Schema Validator, JSON Schema Generator, YAML to JSON Converter, Robots.txt Tester. They run on your own machine; what you paste never reaches the server.

Claude Code

claude mcp add --transport http 17x7 https://api.17x7.com/mcp

Add --scope user to make it available in every project, or --scope project to write it to the repo's .mcp.json.

Hermes Agent

hermes mcp add 17x7 --url https://api.17x7.com/mcp

Or in ~/.hermes/config.yaml:

mcp_servers:
  17x7:
    url: "https://api.17x7.com/mcp"

Claude (web and desktop)

Settings → Connectors → Add custom connector, and paste https://api.17x7.com/mcp. No OAuth step is needed.

Cursor

{ "mcpServers": { "17x7": { "url": "https://api.17x7.com/mcp" } } }

Put that in ~/.cursor/mcp.json, or use the install link cursor://anysphere.cursor-deeplink/mcp/install?name=17x7&config=eyJ1cmwiOiJodHRwczovL2FwaS4xN3g3LmNvbS9tY3AifQ==.

Raw JSON-RPC

curl -s https://api.17x7.com/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"roof_pitch","arguments":{"rise":6,"run":12}}}'

JSON API

Base URL https://api.17x7.com (the same paths also answer on 17x7.com). Send parameters as a query string with GET or as a JSON body with POST. Successful responses look like {"ok":true,"tool":…,"result":{…},"steps":[…],"notes":[…]}; validation problems return HTTP 400 with {"ok":false,"errors":[{"field","message"}]}. The full description is in openapi.json.

MethodPathMain parameters
GET/POST/api/v1/time/converttime, from, to
GET/POST/api/v1/cron/explainexpression, tz, count, from
GET/POST/api/v1/calc/etsy-feesitem_price, shipping_charged, sales_tax, item_cost, seller_country, offsite_ads …
GET/POST/api/v1/calc/amazon-fbaprice, length_in, width_in, height_in, weight_lb, category, product_cost …
GET/POST/api/v1/calc/roof-pitchrise, run | angle, span_ft, length_ft, overhang_in, waste_percent
GET/POST/api/v1/calc/deck-materialswidth_ft, depth_ft, board_width_in, gap_in, joist_spacing_in, fastener …
GET/api/v1/health (or /api/health)—
curl 'https://api.17x7.com/api/v1/calc/etsy-fees?item_price=25&shipping_charged=5&sales_tax=2.4'

Try it

Pick an example and press Send — the request goes to this site's live API.

—

Limits and fair use

  • Anonymous callers: 60 requests per minute per IP; over that you get HTTP 429 with Retry-After.
  • Request bodies up to 64 KB, counted as received, and one JSON-RPC message per MCP request (batches are refused).
  • JSON Schema validation is not part of the API: a schema can describe arbitrarily expensive work, so it runs only in the browser validator, on your own machine.
  • Results are deterministic estimates — the same fee schedules and formulas as the calculators, documented on each calculator page.
  • Found a bug or need a tool that is not here? Tell us.

Discovery files