SpendLens is a free AI spend audit tool for startup founders, engineering managers, and small teams who want to understand whether they are overspending on AI tools. It audits tools like ChatGPT, Claude, Cursor, GitHub Copilot, Gemini, OpenAI API, Anthropic API, and Windsurf, then generates savings estimates, recommendations, and a shareable public report.
Live app: https://spendlens-seven-lovat.vercel.app
SpendLens helps teams:
- enter multiple AI tools, plans, monthly spend, and seat counts
- compare current spend against expected plan costs
- detect oversized plans and inflated spend
- identify overlapping coding assistant tools
- estimate monthly and annual savings
- generate a public shareable audit report
- capture qualified leads after showing audit value
- Next.js
- TypeScript
- Tailwind CSS
- shadcn/ui
- Recharts
- Vitest
- Vercel
- OpenAI API support with fallback
- Resend email support with fallback
Users can add multiple AI tools and enter the plan, monthly spend, and number of seats for each tool.
The audit engine checks:
- expected plan cost vs entered spend
- small-team enterprise overkill
- Cursor + GitHub Copilot overlap
- high API spend credit opportunities
- savings priority level
SpendLens can generate an AI-written executive summary when an OpenAI API key is available. If no API key is configured or the request fails, it falls back to a rule-based summary so the product remains stable.
After the user sees value, SpendLens asks for email, company, and role to send the full report. This keeps the lead gate after the audit result instead of blocking value upfront.
Each captured audit gets a public report URL at:
/report/<audit-id>
The public report avoids showing private lead details.
Abuse protection
The lead form includes a honeypot field to reject basic bot submissions.
Quick Start
Install dependencies: npm install
Run the development server: npm run dev
Open: http://localhost:3000
Run lint: npm run lint
Run tests: npm test
Run production build: npm run build
Environment Variables
The app works without these variables by falling back safely, but these can be configured for production behavior:
OPENAI_API_KEY= RESEND_API_KEY= NEXT_PUBLIC_APP_URL= OPENAI_API_KEY
Used to generate the personalized audit summary. If missing, SpendLens uses a fallback rule-based summary.
RESEND_API_KEY
Used to send transactional audit confirmation emails. If missing, the app still captures leads and reports successfully.
NEXT_PUBLIC_APP_URL
Used in transactional email links.
Example:
NEXT_PUBLIC_APP_URL=https://spendlens-seven-lovat.vercel.app Project Structure app/ api/ leads/ route.ts summary/ route.ts report/ [id]/ page.tsx page.tsx
components/ ui/ audit-form.tsx audit-form-client.tsx audit-report.tsx lead-capture-dialog.tsx spend-chart.tsx
lib/ audit-engine.ts
tests/ audit-engine.test.ts
data/ leads.json reports.json
Decisions
- Rule-based audit math instead of AI-based math
The savings calculations are deterministic and rule-based. This makes the output easier to test, debug, and explain. AI is used only for the executive summary layer, not the financial calculation layer.
- Lead capture after value
The form shows audit results before asking for email. This matches the product goal of building trust before conversion.
- Multi-tool input instead of single-tool calculator
Startups rarely use only one AI tool, so SpendLens supports an AI stack rather than a single subscription.
- Public report pages
Shareable reports make the product more viral and useful for founders or engineering managers who want to share findings internally.
- JSON persistence for prototype speed
For this take-home build, lightweight JSON persistence keeps the project easy to run and review. In a production version, this should move to Supabase, Postgres, or another durable database.
Testing
The audit engine has automated tests covering:
inflated spend detection coding assistant overlap API spend credit opportunity efficient low-cost stack high-priority savings classification
Run:
npm test Deployment
The app is deployed on Vercel:
https://spendlens-seven-lovat.vercel.app Notes
SpendLens is built as a product MVP, not just a coding exercise. The focus is on a complete user flow: audit input, savings logic, results visualization, lead capture, and shareable report output.