Concepts

A brief of the core concepts behind Tessl.

👉 Closed beta notice

The full framework is currently part of Tessl’s closed beta program. You can request access here.

Concept	Definition
Spec-driven development (SDD)	A development approach where specs — not code — are the primary artifact. Specs describe intent in structured, testable language, and agents generate code to match them.
Spec	A Markdown-like file (.spec.md) that defines software intent and capabilities. Specs serve as the source of truth for code generation and collaboration across teams.
Usage spec	A spec that provides usage instructions for existing code, such as open source libraries. It describes how to interact with software dependencies so agents can use them reliably and consistently.
Tessl Spec Registry	A place where you can download public libraries usage specs and also share your own specs with your team.
Tessl Framework	The code that allows humans and your agents to interact with specs and the spec registry for writing code and tests, MCP or CLI based.
Knowledge Index	Refers to the KNOWLEDGE.md file that links to usage specs installed in your project.
Plan	The Tessl Framework converts requested changes to a spec into a plan firt, and while executing it updates the plan accordingly.