面试题库

7 天 MCP：把工具接进任何 Agent

D1 为什么需要一个协议：host / client / server 三角、JSON-RPC 消息与三种原语

• MCP 规范为什么规定一个客户端只连一个服务端？多路复用不是更省资源吗？Why does the MCP spec require one client per server instead of multiplexing many servers over one connection?

  国内高频海外高频进阶#architecture#security

  分析过程 · 先想清楚再作答

  1. 这题看着在问性能，其实在问安全边界。只从连接数和资源占用切入的回答会被判为没读过设计原则那一节。
  2. 拆法：先问「共享一条通道之后，谁能看见谁」。规范写死了两条原则——服务端不应该读到整段对话，也不应该看得见别的服务端；一对一是实现这两条最直接的手段。
  3. 举一个具体后果：接一个第三方天气服务端时，一对一隔离让它只能看到你传的城市名；共享通道则可能让它读到你和内部数据库服务端之间的往来，那就是一次数据泄露。
  4. 结论：完整对话历史留在宿主，服务端只拿到这次真正需要的参数；宿主是唯一的安全边界执行者，也是唯一做跨服务端编排的地方。
  5. 代价要主动说：接 N 个服务端就有 N 条连接、N 套生命周期要管，客户端实现的复杂度大头正是在这里，而不是在发报文上。
  6. 可预期的追问：那多个服务端的工具重名怎么办？答案是聚合与消歧是宿主侧的职责，规范建议加服务端标识前缀，并且明确说不要依赖服务端自报的名字，因为它不保证唯一也未经验证。

  How to reason about it · think before answering

  1. It reads like a performance question but is really about security boundaries. Answering only in terms of connection count signals you never read the design principles.
  2. Ask who can see whom once a channel is shared. The spec fixes two principles: servers should not read the whole conversation, and should not see into other servers. One-to-one is the most direct way to enforce both.
  3. Concrete consequence: with isolation, a third-party weather server sees only the city you passed. On a shared channel it could observe traffic between you and an internal database server — a data leak.
  4. Conclusion: full history stays with the host, each server receives only the arguments this call needs, and the host is the single place where boundaries are enforced and cross-server orchestration happens.
  5. State the cost yourself: N servers means N connections and N lifecycles, and that is where most client complexity lives, not in sending messages.
  6. Likely follow-up: how do you handle tool name collisions across servers? Aggregation and disambiguation belong to the host; the spec suggests prefixing with a server identifier and explicitly warns against relying on the server's self-reported name, which is neither unique nor verified.

  答题要点

  • 一对一是安全设计而非性能设计：服务端读不到整段对话，也看不见别的服务端
  • 完整历史留在宿主，服务端只收到本次调用真正需要的参数
  • 跨服务端的聚合、消歧、授权都由宿主统一做，边界只有一处需要加固
  • 代价是连接与生命周期管理，这是客户端实现复杂度的主要来源

  Key points

  • One-to-one is a security decision, not a performance one: servers cannot read the conversation or see peers
  • Full history stays in the host; a server receives only the arguments for the current call
  • Aggregation, disambiguation, and authorization all happen in the host, so there is a single boundary to harden
  • The cost is connection and lifecycle management, which dominates client implementation complexity