Building a free tool takes anywhere from a weekend to a month. Validating one takes 20 minutes. Anyone who has shipped tools that flopped knows this lesson the hard way: spend the 20 minutes.
Here are the five filters we run any free tool idea through before committing engineering time.
Filter 1: The journalist-cite test
Write a single sentence a journalist or blogger would copy into their article. The sentence should mention the tool by name and reference the specific problem it solves better than alternatives.
Pass: "Validate Stripe webhook signatures with [Tool Name] — the only free validator that doesn't require a Stripe account."
Fail: "Use [Tool Name] to manage your business better."
If you can't write a pass sentence, the tool has no linkable hook. Stop here.
Filter 2: Search demand reality check
Type the primary keyword you want to rank for. Look at the top 10 results. Three signals matter:
- No tools in the top 10: Pure opportunity. Whatever ranks #1 today is beatable with a real tool.
- One dominant tool plus a long listicle tail: Beatable if you have a clear angle on what the dominant tool misses.
- Three or more well-funded tools in the top 10: Either find a different angle or move on. You're not going to outrank Cloudflare's free tools.
If the SERP has no obvious search demand at all — keyword volume is zero in your favorite keyword tool — the tool will rank fine but earn nothing because nobody searches for it.
Filter 3: The output-sharing test
Imagine the tool finished. A user has run it and gotten a result. Can they:
- Screenshot the result and post it on Twitter?
- Paste the result into a Slack thread or email?
- Embed the result in a blog post?
If the output is just a number, "0.847" isn't shareable. If the output is "0.847 — which means your site is in the bottom 25% of pages for E-E-A-T signals because [specific reasons]" — now it's shareable.
The most linkable tools have shareable outputs by design. Add context, comparisons, and a memorable hook to every result.
Filter 4: The build-vs-clone test
If a competitor saw your tool succeed, could they clone it in a weekend? If yes, the tool has no defensible moat. Linkable doesn't mean defensible, and that's fine for some tools — but knowing the difference matters.
Three kinds of moats work:
- Data moat: Tool depends on data you have and they don't (proprietary, scraped, partnered).
- Domain moat: Tool requires expertise to build correctly — a regex linter built by people who actually understand regex is harder to replicate than it looks.
- Distribution moat: You earned the early links before they could; even an inferior clone struggles to overtake established backlink profiles.
Tools with no moat still earn links, but plan for someone to copy you eventually.
Filter 5: The first-100-users test
How will the first 100 users find the tool in the first 7 days after launch? Three real channels with real audiences, not "post on social media."
Realistic answers:
- "Show HN post — the tool fits the HN aesthetic of solving a specific developer problem"
- "Submit to ProductHunt on Tuesday — there's no other AI-readability scorer launched recently"
- "Email Lenny's Newsletter — he covers PM tools and this fits his beat"
- "Post in r/SaaS — they upvote utility tools from small founders"
Unrealistic answers:
- "Twitter and LinkedIn"
- "SEO over time"
- "Word of mouth"
If you can't name three concrete launch channels with specific audiences, you don't have a distribution plan. The tool will exist but nobody will find it.
A worked example
Idea: "Free fluff detector — analyzes blog posts for filler words and AI-generated patterns."
Filter 1: "Spot AI-generated content with the free fluff detector — checks for filler phrases, passive voice, and the 20 most common LLM patterns." Passes.
Filter 2: "fluff detector" has 1,000+ monthly searches, SERP is dominated by one Grammarly-style competitor with weak coverage of AI patterns. Pass — clear angle.
Filter 3: Output is "Fluff score: 67/100 — found 14 filler phrases including 'in today's fast-paced world.'" Shareable. Pass.
Filter 4: Building it requires a curated list of patterns refined by people who've written a lot. Possible to clone but the pattern library is the moat. Pass.
Filter 5: r/copywriting, r/freelancewriting, r/SEO, Marketing Brew newsletter, Animalz blog. Five real channels. Pass.
Result: ship it. This is roughly the validation that led to our own fluff detector.
What this saves you
Most tools that fail are ones that would have failed these filters. Run them before writing code. The opportunity cost of building the wrong tool is real — a month of engineering time on a tool nobody links to is a month not spent on something that would have earned 100 links.
We built the free tool ideas generator to surface ideas that already pass most of these filters automatically — each suggestion comes with a linkable hook, search queries it solves, and a distribution plan. Useful as a starting point even if you end up running your own validation.
The summary: validate fast, build only what passes, distribute everything you build.
