Explore · The library

Every resource founders actually use, in one library.

The essays, videos, podcasts, books and tools behind every answer across eChai's hubs, from starting up to go-to-market, D2C, founder money and AI, each with a note on why it is here.

What founders use most, ranked by how many answers lean on it.

  1. Product-builder-oriented leaderboard that maps benchmark scores to practical use cases. vellum.ai Tool · How Founders Use AI Vellum LLM Leaderboard Vellum
  2. Fastest way to sanity-check what any model actually costs before you wire it in. pricepertoken.com Tool · How Founders Use AI Price Per Token leaderboards Price Per Token
  3. Open-source, config-file evals that run in CI; used by OpenAI and Anthropic themselves. github.com Tool · How Founders Use AI Promptfoo Promptfoo
  4. Validate and auto-retry model outputs against a schema; 6M downloads a month for a reason. github.com Tool · How Founders Use AI Instructor: structured outputs for LLMs Jason Liu (567 Labs)
  5. Open-source programmable rails: topic control, fact-checking, and jailbreak detection. github.com Tool · How Founders Use AI NeMo Guardrails NVIDIA
  6. A hub of pre-built validators that intercept bad inputs and outputs before users see them. github.com Tool · How Founders Use AI Guardrails AI Guardrails AI
  7. Automatically probe your own app for injection and PII leaks before attackers do. promptfoo.dev Tool · How Founders Use AI OWASP LLM Top 10 red-teaming with Promptfoo Promptfoo
  8. The leading open-source LLM observability platform: traces, costs, evals, and prompt management. langfuse.com Tool · How Founders Use AI Langfuse Langfuse
  9. The managed alternative, strongest if you already build on LangChain. langchain.com Tool · How Founders Use AI LangSmith Observability LangChain
  10. A living library of proven deep research prompts across OpenAI, Gemini and Qwen. github.com Tool · How Founders Use AI awesome-deep-research-prompts (GitHub) LangGPT community
  11. Categorizes why people got caught (time pressure, lack of training), a mirror for your own habits. naturalandartificiallaw.com Tool · How Founders Use AI AI Hallucination Cases Tracker (international) Natural & Artificial Law
  12. The underlying repo with papers, notebooks and lessons for going deeper. github.com Tool · How Founders Use AI dair-ai/Prompt-Engineering-Guide (GitHub) DAIR.AI
  13. Type a product URL, get a structured competitor matrix in minutes; a fast first pass. competely.ai Tool · How Founders Use AI Competely: Instant AI competitive analysis Competely
  14. A free-to-start tool built specifically for solo founders' competitor scans. founderpal.ai Tool · How Founders Use AI AI Competitor Analysis for Busy Founders FounderPal
  15. The documented incident record, plus a searchable database of similar AI mishaps. incidentdatabase.ai Tool · How Founders Use AI AI Incident Database: Samsung Data Leak (Incident 768) AI Incident Database
  16. A free workflow that finds competitors and files structured profiles into Notion automatically. n8n.io Tool · How Founders Use AI Automate competitor research with Exa.ai, Notion and AI agents (n8n template) n8n community
  17. Set-and-forget monitoring so pricing page changes come to you instead of you checking weekly. n8n.io Tool · How Founders Use AI Monitor competitors' websites for changes with OpenAI and Firecrawl (n8n template) n8n community
  18. Purpose-built for the hardest part: keeping competitor pricing data actually current. n8n.io Tool · How Founders Use AI Automated competitor pricing monitor with Bright Data MCP & OpenAI (n8n template) n8n community
  19. Combines scraping, RSS, and an LLM into a continuous competitor intelligence feed. n8n.io Tool · How Founders Use AI AI-driven competitor & market intelligence with GPT-4 & Apify (n8n template) n8n community
  20. A free AI calculator to generate a first-draft TAM/SAM/SOM you then verify. founderpal.ai Tool · How Founders Use AI AI Market Size Calculator (free, no email) FounderPal
  21. Structured inputs stop you from letting the AI invent the assumptions. pmtoolkit.ai Tool · How Founders Use AI Free TAM SAM SOM Calculator: Investor-Ready Market Sizing in 10 Minutes PM Toolkit
  22. Paste your interview questions and it flags the leading ones before you embarrass yourself. momtest.ai Tool · How Founders Use AI MomTestAI: Validate Customer Discovery Questions MomTestAI
  23. Converts Reddit threads, search data, and YouTube signals into scored startup ideas daily. ideabrowser.com Tool · How Founders Use AI Ideabrowser Greg Isenberg
  24. Pre-mined pain points from Reddit, G2, Capterra, and app stores if you want to skip the scraping. bigideasdb.com Tool · How Founders Use AI BigIdeasDB: The Startup Ideas Database From 1M+ Real Complaints BigIdeasDB

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The hubs

Starting Up Find an idea, validate it, build, and land your first customers. 1327 questions GTM Go-to-market, from breaking in to how the best teams do it. 379 questions D2C Building a direct-to-consumer brand, India-first. 512 questions Wealth Paying yourself, ESOPs, secondaries, and de-risking founder wealth. 165 questions How Founders Use AI How founders actually put AI to work, mapped topic by topic. 360 questions Glossary Plain-language definitions of the startup and VC terms you'll hit. 425 terms
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