Spec Driven Development: API Design First with GitHub Spec Kit and Specmatic MCP

I first came across Specification Driven Development (SDD) when I was exploring AWS Kiro. Coming from an Extreme Programming (XP) background (TDD, small batches, and fast feedback), SDD clicked instantly and it directly tackles the intent-vs-implementation drift of “vibe coding”. By capturing intent up-front, then letting agents help with implementation, we can avoid deviation from what we meant. Github Spec Kit (open source ) also delivers this SDD workflow and there is really no excuse not to try it.

In an earlier write-up, I shared about “Guardrails for API Development: Guiding Coding Agents with Specmatic MCP“. Here I had already provided the API specification as well as detailed instructions via Claude mark down files for Claude Code to build out the app. That one-shot demo looks cool, but real-world delivery is iterative, our API and system design evolve, while fundamentals (compatibility, contracts, resiliency) need to be firm.

Spec-Driven Development gives structure to agentic software delivery. With Spec Kit guiding the workflow and Specmatic MCP providing API guardrails, you get fast iteration and alignment to intent. This was a tiny demo, your gates, checks, and branching model can (and should) reflect your engineering standards.