MCP servers and skills both extend a coding agent. When do you reach for each, and what goes in the project instruction file instead?

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

Interview Bank

328 questions total; 1 shown with current filters.

CourseAll From Frontend Engineer to Agent Engineer in 30 Days Prompt Engineering From Scratch in 5 Days Mastering Claude: From Conversation to Claude Code in 5 Days Mastering Codex and the OpenAI Agents SDK in 5 Days MCP in 7 Days: Wire Tools Into Any Agent Agent Skills in 7 Days: Turn Experience Into Reusable Capability Context Engineering in 5 Days RAG in 14 Days: From Retrieval to Trustworthy Answers Build an AI Short-Drama Production Pipeline With Agents in 14 Days

WeekAll W1

MarketAll Common in China Common overseas

DifficultyAll Basic Intermediate Deep dive

Mastering Codex and the OpenAI Agents SDK in 5 Days

D2 Codex, Level Up: Cloud Tasks, Code Review, MCP Integration, Custom Instructions, IDE Integration

MCP servers and skills both extend a coding agent. When do you reach for each, and what goes in the project instruction file instead?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？
Common in ChinaCommon overseasBasic#mcp#skills#coding-agent
How to reason about it · think before answering
This tests separation of abstraction levels, the tooling-side version of the increasingly common 'function calling vs MCP vs skills' question.
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.
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.
Conclude: rules in the instruction file, external systems via MCP, procedures as skills; keep each fact in one place to avoid contradictions.
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.
分析过程 · 先想清楚再作答
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。
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。
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。
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。
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。
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
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