Your product is my marketing opportunity: is this free tool worth building?
Paste what your company sells - who buys, the deal size, how many leads become customers - and your notes on one free-tool idea: what it does, the keyword and its searches, the tools that already exist, the build estimate, the upkeep, the traffic you expect and how you would capture leads. Your browser works out what a lead is worth, the first year's lead value against the build and upkeep, the payback and the leads a month it needs, and flags the pitfalls. Free, before you sign in, and nothing is uploaded. Then the score lane rates the skill's eight factors and says build, build smaller or don't build, and the plan lane scopes the first version.
The companies, people and numbers in the examples are invented. Three are scores (build, build smaller and don't build; the calculator also carries its plan, one click after the score) and one is a plan; each comes with a saved model reply, so you can see the whole page without signing in or spending a credit.
What this does, and what it does not
A free tool is the most durable marketing asset a small team can build: HubSpot's Website Grader took 2 engineers and 2 weeks, and Unsplash took 3 hrs. It is also the easiest to overbuild. A grader with accounts, dashboards and a crawler is a product nobody pays for, a calculator nobody searches for is a page nobody finds, and a tool with no path to what you sell earns traffic but not pipeline. The skill's answer is to pick a tool your buyers already need, next to your product, that does one thing; to check that a lead's value times the leads it can bring beats the build plus the upkeep; to choose the gate on purpose; and to judge it on leads, qualification rate and trial or signup conversion, never on visitors. This page does the arithmetic it can from your notes and shows how it got each number.
The paid lanes see your description and your tool notes (each cut in the middle past a few thousand characters, and the page says so), your own scores if you gave them, and the page's math and flags. Your input stays in this browser unless you run a lane. Every reply is held to your input: quotes are checked word for word, and no cost, count, rate, date or duration may be invented - missing ones are written as [placeholders]. It does not research keywords, look up search volumes or build the tool; bring what you know. Derived from the agent skill @coreyhaines31/free-tools by Corey Haines (coreyhaines31/marketingskills, MIT) and its references: the four core principles, the six tool types, the validation questions, the four gating options, build versus no-code versus embed, the minimum viable tool, the eight-factor scorecard, the four pitfalls and the case library. Sources are listed in llms.txt.