Tutorial: Building Paid AI APIs with x402 on Stacks

Summary

Add a comprehensive tutorial on building paid AI APIs using the x402 payment protocol on Stacks. This fills a gap in the current AI use case documentation which only shows code snippets without end-to-end implementation guidance.

Problem

The current AI use cases page shows x402-Stacks code snippets but lacks:

• Step-by-step tutorial on building complete APIs
• Payment middleware configuration examples
• Client integration patterns
• Pricing strategies and best practices
• Production deployment guidance

This is a high-impact gap for developers building agent-to-agent payment systems and AI service monetization.

Solution

I've created a complete working example with merge-ready tutorial content:

Repository: https://github.com/bastiatai/x402-ai-api

What's Included

1. Complete Working Code

   • Express.js server with x402 payment middleware
   • Three example AI endpoints (sentiment, summarization, extraction)
   • Automatic payment client using axios interceptor
   • TypeScript with full type safety

2. Comprehensive Tutorial (TUTORIAL.md)

   • Part 1: Understanding x402 protocol
   • Part 2: Project setup
   • Part 3-4: Server and client implementation
   • Part 5: Configuration
   • Part 6: Testing
   • Part 7: Pricing strategies (fixed, tiered, dynamic)
   • Part 8: Production deployment
   • Part 9: Advanced patterns (error handling, rate limiting, webhooks)

3. README with Quick Start

   • Installation instructions
   • API endpoint documentation
   • How it works explanation
   • Production considerations

Tutorial Quality

• ✅ Production-ready code that compiles and runs
• ✅ Step-by-step with code examples
• ✅ Explains WHY x402 matters (vs traditional API monetization)
• ✅ Covers common issues and solutions
• ✅ Includes next steps and resources
• ✅ Positioned for agent-to-agent economy use case

Suggested Placement

Add tutorial link to:

1. docs/build/get-started/use-cases/ai.md - under x402-Stacks section
2. Create new tutorial page: docs/build/tutorials/x402-ai-api.md

Tutorial Content

The tutorial is ready to merge as-is from the repository, or I can provide it as a markdown file for direct inclusion in the docs repo.

Why This Matters

x402 enables emerging use cases like:

• AI agents paying other AI agents for services
• Pay-per-use API monetization without intermediaries
• Building the agent economy on Bitcoin-secured infrastructure

This tutorial makes these patterns accessible to developers building on Stacks.

Files Available

• TUTORIAL.md - Complete step-by-step tutorial (ready to merge)
• README.md - Quick start guide
• src/server.ts - Working server implementation
• src/client.ts - Working client implementation

Let me know if you'd like me to submit a PR with the tutorial content or if you prefer to review and adapt it directly.

---

Related: Addresses the gap in AI use case documentation noted in the current docs structure. Complements existing x402-Stacks code snippet with full implementation guidance.

Review docs/build/get-started/use-cases/ai.md and the proposed docs/build/tutorials/x402-ai-api.md location. Read TUTORIAL.md, README.md, src/server.ts, and src/client.ts in the linked repository, then verify that the adapted tutorial covers setup, implementation, testing, pricing, and deployment before linking it from the AI use cases page.