Rules, Skills, MCP, Workflows, and Memory in AI coding agents: a field guide built from real tasks
AI coding agents now expose five overlapping configuration systems, and each product names them differently. Getting the boundaries wrong means bloated context, gated workflows that never run, and secrets leaking through logs; getting them right keeps an agent useful across Claude Code, Codex, and Pi without maintaining three divergent setups.
The five configuration concepts every AI coding agent exposes—Rules, Skills, MCP, Workflows, and Memory—get conflated by overlapping product naming. This guide separates them by what they actually solve: Rules enforce persistent conventions, Skills package a repeatable task's method, MCP connects external tools and data, Workflows sequence steps with confirmation gates, and Memory preserves confirmed decisions across sessions.
Working examples ground each concept: a Figma-to-COS image pipeline that combines a Skill with an MCP connection, a `CLAUDE.md` rule set that stops scope creep and fake test results, and a page-check Skill with progressive disclosure. A Chrome DevTools MCP setup shows the permission layers and tab-hijacking issues that surface when connecting an agent to a live browser.
Product differences matter. Claude Code uses `CLAUDE.md` and supports `AGENTS.md` conditionally; Codex uses `AGENTS.md` and `$skill` invocation; Pi-Bolt uses `/skill:name` and supports shared `~/.agents/skills/` paths. The advice is to share Skill content across tools, adapt host-specific behavior, and verify by real task runs rather than config checklists.
The overlapping names across products are not an implementation detail but the original problem: a developer cannot learn one tool's mental model and transfer it. Each product's load timing, maintenance method, and execution behavior differ even when the concept name matches.
Memory is the most oversold concept: a file named MEMORY.md neither guarantees the model reads it each time nor proves content correctness. Retrievability must be tested in a fresh session, which is a concrete acceptance criterion most agent configuration lacks.
The practical advice to share Skill content across tools while adapting host-specific behavior reveals a real cost: the more tools you run, the more divergence you maintain. A shared directory plus per-tool links is only a partial answer, since load semantics still differ.
The Chrome DevTools MCP debug story shows agent tooling still sits at the integration layer: permission models, browser sessions, and connection reuse are unresolved enough that a custom adapter script carrying background-creation parameters is needed to make the tool usable.