spec

spec is where the agent is actually defined. It carries three required blocks and a long list of optional ones.

Required

Field	Reference
capabilities	capabilities
server	server
language	language

Optional

Field	Reference
card	card
agent	agent - provider, model, prompt
config	config
services	services
acronyms	acronyms
tools	tools
skills	skills
artifacts	artifacts
hooks	hooks
scm	scm
development	development
deployment	deployment

Minimal valid spec

The three required blocks together are enough to pass validation:

spec:
  capabilities:
    streaming: true
    pushNotifications: false
    stateTransitionHistory: false
  server:
    port: 8080
  language:
    go:
      module: github.com/example/agent
      version: "1.26"

Everything beyond that is opt-in - pull in only what your agent actually uses. The schema doesn't penalise you for omitting capabilities you don't need; it penalises ambiguity.