Why this exists
Skills, agents, and teams are the right granularity for agent tooling, but no one was shipping them as actually-distributable artifacts. n3 is the boring-but-necessary registry layer that turns them into installable things.
What it does
Defines four first-class types — agent, skill, team, app bundle — as JSON schemas. Ships a registry (harness-library), a validator (scripts/validate.py), and a bootstrap installer. An end user runs one command to pull a skill into their environment.
What I learned
Schemas are more important than code. Once the schema was right, the registry, validator, and installer all collapsed into small surfaces. The projects I spent most time on were the ones where I got the schema wrong first.