Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add jeffreytse/grimoire-core --skill apply-product-market-fit-testgit clone --depth 1 https://github.com/jeffreytse/grimoire-coreWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/jeffreytse/grimoire-core/apply-product-market-fit-test)<a href="https://agentmods.dev/skills/jeffreytse/grimoire-core/apply-product-market-fit-test"><img src="https://agentmods.dev/badge/skills/jeffreytse/grimoire-core/apply-product-market-fit-test/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/jeffreytse/grimoire-core/apply-product-market-fit-test"><img src="https://agentmods.dev/badge/skills/jeffreytse/grimoire-core/apply-product-market-fit-test.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00093 | $0.01769 |
| Opus 5.5 | $0.00037 | $0.00708 |
| Sonnet 5.5 | $0.00019 | $0.00354 |
| Haiku 4.5 | $0.00009 | $0.00177 |
Grade A, and why
apply-product-market-fit-test scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 65 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Apply Product-Market Fit Test
Survey active users with Sean Ellis's "how would you feel if you could no longer use this product" question and treat 40%+ answering "very disappointed" as the threshold before investing in growth, sales, or scaling — rather than relying on founder intuition or vanity metrics — because premature scaling before this threshold is met is the leading documented cause of early-stage startup failure.
Why This Is Best Practice
Sean Ellis, "Find Your Product/Market Fit Before Scaling" (2009): Developed a standardized survey — asking active users "How would you feel if you could no longer use [product]?" with options Very disappointed / Somewhat disappointed / Not disappointed / N/A — and established, through testing across many startups he advised, that a result of 40% or more answering "very disappointed" reliably distinguished companies ready to scale from those still needing product iteration.
Marc Andreessen, "The Only Thing That Matters" (2007): Provides the qualitative complement to Ellis's quantitative test — describing product-market fit as a state a founder can feel operationally: usage growing faster than the team can serve it, servers strained by organic demand, press and word-of-mouth pulling in customers without paid acquisition, and hiring struggling to keep pace with demand. Andreessen's essay argues market — not team or product execution alone — is the dominant variable in early-stage outcomes, and that fit with that market is legible through these observable symptoms.
Marmer, Herrmann, Dogrultan & Berman, "Startup Genome Report" (2011): A large-scale study of startup failure patterns identified premature scaling — hiring, spending on paid acquisition, or expanding operationally before validating fit — as the single most common documented cause of early-stage failure, and found it strongly correlated with skipping or ignoring a product-market fit check like Ellis's test.
Why best: Revenue growth, signup counts, and funding raised are frequently used as informal proxies for "the product is working," but none of them specifically measure whether users would suffer from the product's disappearance — which is the precise signal Ellis's test is built to surface, and the signal Andreessen's qualitative symptoms independently corroborate. A startup can show growth on vanity metrics while still lacking the underlying fit that makes further scaling investment pay off.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 4d ago First seen · 65 lines · 93 tokens per session scan A 6c3e5ec86885
apply-product-market-fit-test is a skill published in the GitHub repository jeffreytse/grimoire-core (5 stars, last pushed 5d ago), licensed MIT. It adds 93 tokens to every session and 1,769 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-17.
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