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• MCP server 和 skill 都是在给 coding agent 加能力，什么时候该用哪一个？项目说明文件又放什么？MCP servers and skills both extend a coding agent. When do you reach for each, and what goes in the project instruction file instead?

  国内高频海外高频基础#mcp#skills#coding-agent

  分析过程 · 先想清楚再作答

  1. 这题考的是抽象层次的区分，是国内面试开始高频出现的「Function Call / MCP / Skills 三者区别」的工具侧版本。
  2. 拆法是问「加的是什么」：加的是访问外部系统的能力（查工单、读数据库、调内部服务）就是 MCP，它是协议层的工具；加的是一套多步骤的做法（发版检查、迁移流程）就是 skill，它是提示词层的流程包；每次会话都要遵守的约定就是项目说明文件。
  3. 再给触发方式的差别：MCP 工具由模型在需要数据时调用；skill 由用户显式点名或由模型按描述匹配；说明文件每次会话开头无条件读入。
  4. 结论落到一句话：规矩归说明文件、外部系统归 MCP、流程归 skill；同一件事只放一处，避免三处互相矛盾。
  5. 可预期的追问：skill 里能不能调 MCP 工具？可以，skill 的步骤里可以要求使用某个工具，两者是正交的层次，不是替代关系。

  How to reason about it · think before answering

  1. This tests separation of abstraction levels, the tooling-side version of the increasingly common 'function calling vs MCP vs skills' question.
  2. Ask what is being added: access to an external system (tickets, databases, internal services) is MCP, a protocol-level tool; a multi-step procedure (release checklist, migration flow) is a skill, a prompt-level workflow package; conventions to obey every session belong in the instruction file.
  3. Contrast triggers: MCP tools are invoked by the model when it needs data; skills are invoked explicitly by name or matched by description; instruction files are loaded unconditionally at session start.
  4. Conclude: rules in the instruction file, external systems via MCP, procedures as skills; keep each fact in one place to avoid contradictions.
  5. Expect the follow-up: can a skill use MCP tools? Yes; a skill's steps can call for a tool, the layers are orthogonal, not substitutes.

  答题要点

  • MCP 加的是访问外部系统的工具，由模型按需调用
  • skill 加的是多步骤流程，由用户点名或按描述匹配触发
  • 项目说明文件放每次会话都要遵守的约定、禁区与环境事实
  • 三者正交：规矩、外部系统、流程各放一处，skill 里可以要求用某个 MCP 工具

  Key points

  • MCP adds tools that reach external systems, invoked by the model on demand
  • Skills add multi-step procedures, triggered by name or matched by description
  • The instruction file holds conventions, no-go areas and environment facts read every session
  • The three are orthogonal: rules, external systems, procedures each live in one place; a skill may call for an MCP tool