The private agent stack has six layers.
Building AI agents becomes reliable when each layer answers a practical question: what job is this agent doing, what judgment should guide it, what knowledge may it use, which tools can change the world, which skills make the work repeatable, and where does a human review the trace?
01
Start with one job contract
Choose one workflow a real person already repeats: research a topic, prepare a release, review a proposal, qualify a lead, or repair a failed task. Write the success condition, inputs, forbidden actions, budget, and the point where the assistant must stop and ask.
02
Give the agent a philosophy
A private assistant needs judgment rules, not only instructions. Define what careful work means, how to handle uncertainty, which tradeoffs are acceptable, and when safety, privacy, money, or public reputation require human ownership.
03
Build the knowledge layer
Move trusted notes, documents, examples, decisions, and source material into a private knowledge space. The agent should retrieve and cite what you gave it, record useful decisions, and avoid guessing from stale memory.
04
Add MCP tools deliberately
Give the assistant tools only after the job boundary is clear. Each tool needs a readable name, a narrow schema, visible invocation, expected output, retry rule, and confirmation point for actions that change external state.
05
Package repeatable skills
Turn good work into procedures: research, compare, write, deploy, verify, recover, and hand off. A skill should carry the checklist, scripts, examples, and failure notes that keep the next run from starting over.
06
Route models and review
Use a stronger model for planning and review, a faster route for routine execution, and a checkpoint before public, paid, destructive, identity, security, or irreversible actions. The agent is useful when the trace is reviewable.