Glossary Spec-Driven Development
Spec-Driven Development
Also known as:
sdd, spec driven development, specification-driven developmentPracticesAgentic
Definition
Writing a structured specification (requirements, acceptance criteria, constraints) before implementation, and treating it as the source of truth that code, tests and AI coding agents work from
It gained a name with coding agents: a spec is how you give an agent a goal it can check itself against, instead of a prompt it can only interpret. Tooling such as GitHub's Spec Kit (2025) structures the loop as specify, plan, tasks, implement. The spec is revised when the understanding changes, not quietly outgrown by the code.
The repository's own versions: a PRD (the prd skill), issues written with acceptance criteria, and the to-spec skill. See also documentation-driven development, which starts from the reader's page rather than the requirement.