MCP

Previous article: Day 5 | Tools as Interface: Built-in, Extensions, Services. Now that you know the three kinds of tools and how to pick a layer, this exercise walks you through installing a new tool with your own hands. This is an L3 exercise article. Navigation for subsequent articles: Day Type Topic Day 7 Backbone Meta-Architecture: Everything is a Plugin Day 8 Backbone Memory, Traces, and Observability Day 9 Exercise Graduation Project: Build a Team-Level CI/CD Automation Harness Day 10 Phase Summary L3 Graduation Assessment + Harness Future Trends The Third Time You Repeat It, Make It a Tool Think about your daily routine for a second. In your agent sessions, do you keep piecing together the same bash command? Checking logs, searching rules, exporting data. Every time, the agent has to guess the parameters all over again and hit the same pitfalls. ...

Previous article: Day 4 | Rewrite Your AGENTS.md and Add Your First Interception Hook. Now that you’ve got constraints locked down, we turn to another core question: how should an Agent’s tools be designed? This is an L3 backbone article. Navigation for subsequent articles: Day Type Topic Day 6 Exercise Add a New Tool to Your Agent Day 7 Backbone Meta-Architecture: Everything is a Plugin Day 8 Backbone Memory, Traces, and Observability Day 9 Exercise Graduation Project: Build a Team-Level CI/CD Automation Harness Day 10 Phase Summary L3 Graduation Assessment + Harness Future Trends A Neglected Fact Over the first four posts we finished two phases: Day 0 built our overall understanding of Harness; Day 1 dissected the essence of the Agent Loop. Then we entered the constraint phase—Day 2 cut away what we didn’t need, Day 3 used contracts and Hooks to keep the Agent in check, and Day 4 had us actually restructure a real project. We constrained the Agent thoroughly. It stopped running wild. ...

The previous article, From Scars to Armor: Harness Engineering in Practice, ended with Aristotle having a streamlined router (SKILL.md compressed from 371 lines to 84), an on-demand progressive disclosure architecture, and a working reflect→review→confirm workflow. But one thread never got pulled: Where do confirmed rules actually live? This article follows that thread. It wasn’t planned from the start. Three concrete problems in actual use forced the design out, step by step. ...