Build agents

Build your domain-specific harness with the framework’s components and defaults. Its integrated runtime executes that harness and records progress. Start with one model-only agent and a clear observable job. Add a capability when the job requires it. The authoring guide is the complete supported implementation loop.

Requirement	Guide
Choose a model service	Providers and reasoning
Validate a structured result	Structured output
Call application code	Tools and tool effects
Pause for a person’s decision	Approvals and input and human attention
Reconstruct service-backed tools	Service tools
Perform durable external changes	Durable operations
Shape context and knowledge	Context and memory
Queue work or coordinate steps	Tasks and workflows
Use files, commands or network access	Environments and files and artifacts
Connect externally exposed tools	MCP
Add search, fetch or browser capabilities	Web and browser evidence
Coordinate cooperating agents	Tasks and workflows and collaboration evidence
Deliver repository changes	Git and GitHub evidence
Complete work against independent acceptance	Verified work
Build a product UI	Application UI

Use Python reference for exact types and signatures. The installed cayu guide authoring#cayu-map selects the smallest version-matched local reference for a capability.