Lenny Skills is a collection of product-management and engineering workflows for Claude Code and other AI agents, covering areas such as strategy, research, planning, shipping, growth, and hiring. Each skill gives an agent specialized guidance, frameworks, checklists, or templates for product work, and the catalogue contains many of these skills.
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 RefoundAI/lenny-skills --skill marketplace-fundamentalsgit clone --depth 1 https://github.com/RefoundAI/lenny-skillsWrote 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/refoundai/lenny-skills/marketplace-fundamentals)<a href="https://agentmods.dev/skills/refoundai/lenny-skills/marketplace-fundamentals"><img src="https://agentmods.dev/badge/skills/refoundai/lenny-skills/marketplace-fundamentals/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/refoundai/lenny-skills/marketplace-fundamentals"><img src="https://agentmods.dev/badge/skills/refoundai/lenny-skills/marketplace-fundamentals.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00033 | $0.01582 |
| Opus 5 | $0.00016 | $0.00791 |
| Sonnet 5 | $0.00007 | $0.00316 |
| Haiku 4.5 | $0.00003 | $0.00158 |
Grade A, and why
marketplace-fundamentals 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 12d 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- marketplace-fundamentals — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 88 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Marketplace Fundamentals
Build, bootstrap, and scale a self-sustaining ecosystem of buyers and sellers.
Help the user with marketplace fundamentals using insights from 7 guests and posts across Lenny's Podcast and Newsletter.
How to Help
- Diagnose the stage - Identify if the user is in the bootstrapping, liquidity-seeking, or scaling phase of their marketplace.
- Pinpoint the hard side - Help the user determine which side of the market (supply or demand) is the primary constraint and needs focus.
- Evaluate the value proposition - Assess if the platform offers a 10x improvement in convenience, price, or variety compared to traditional alternatives.
- Select a growth strategy - Recommend specific tactics like single-player mode, geographic constraints, or category niches to build density.
Core Principles
Nail the Value Exchange First
Benjamin Lauzier: "If you don't have product market fit, and if you don't have a good enough growth strategy for at least one side of your marketplace, just forget about all this marketplace stuff. Focus on this core exchange of value, go deep with one side of the marketplace and see if you can rely on some crutch, some hack for the other side for time being."
Before focusing on complex economic ratios, ensure the core transaction provides enough value to both sides to sustain a growth strategy. Identify the most difficult side of the market to acquire and concentrate early resources there.
Build Standalone Value
Ramesh Johari: "The moral is a marketplace business never starts as a marketplace business, because what we think of as a marketplace business is something which at scale is removing the friction of the two sides finding each other. But when you start, you don't have that scale."
Marketplaces struggle at low scale, so you must offer a high friction utility problem that provides value before critical mass is reached. This helps bootstrap the network by giving users a reason to join without existing liquidity.
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 12d ago First seen · 88 lines · 33 tokens per session scan A 061cefc70162
marketplace-fundamentals is a skill published in the GitHub repository RefoundAI/lenny-skills (1,321 stars, last pushed 1mo ago), licensed MIT. It adds 33 tokens to every session and 1,582 once invoked, about $0.0002 per session on Opus 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 2026-08-30.
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