Question 1

What is the Model Context Protocol (MCP) and what problem does it solve?

Accepted Answer

**Target Audience:** Engineers who have used tool calling and keep hearing "just ship an MCP server", and anyone preparing for an AI engineering interview.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (both examples, identical output). Protocol details were checked in October 2026 against the published SDK packages themselves: `@modelcontextprotocol/sdk` 1.32.1 (the v1 line, spec up to 2025-11-25), `@modelcontextprotocol/server` and `@modelcontextprotocol/core` 2.3.1

Question 2

Tool calling vs function calling vs structured output — what changed in 2025?

Accepted Answer

**Target Audience:** Engineers who keep meeting three overlapping names in docs, SDKs and interviews and want one clear mental model plus an accurate timeline.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (the wire-format adapter below, run against canned API responses). Dates and API shapes are cited inline with their source, checked October 2026. The title says 2025; this answer covers 2025 and notes what has changed since.

> **How to read this doc:** Every idea is

Question 3

How do you design good tool definitions for an LLM?

Accepted Answer

**Target Audience:** Engineers turning a backend (REST endpoints, database queries, internal scripts) into tools for an LLM or agent, and anyone who has watched a model pick the wrong tool.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (a tool-definition linter and a tool-selection eval). Vendor guidance is quoted from the Claude docs ("Define tools", "Handle tool calls"), Anthropic engineering posts and other sources as cited, checked October 2026.

> **How to read th

Question 4

How should an agent handle tool errors, timeouts and retries?

Accepted Answer

**Target Audience:** Engineers putting an agent in front of real APIs, where things fail every day, and anyone asked to explain how an agent stays reliable when its tools do not.
**Difficulty:** Hard
**Verified with:** Node 22.22.0 and Python 3.12.3 (both examples below, identical output). Error-result formats were checked in October 2026 against the Anthropic "Handle tool calls" docs page and the MCP tools specification (modelcontextprotocol.io).

> **How to read this doc:** Every idea is expla

Question 5

MCP authoring: how do you build a Model Context Protocol server in 2025-26?

Accepted Answer

**Target Audience:** Engineers asked to expose a product or internal system to AI hosts through MCP, and candidates who need to talk through the build end to end.
**Difficulty:** Hard
**Verified with:** Node 22.22.0 and Python 3.12.3 (both examples, identical output). SDK facts were read in October 2026 from the published packages: `@modelcontextprotocol/server` 2.3.1, `@modelcontextprotocol/core` 2.3.1, `@modelcontextprotocol/node` 2.1.1, `@modelcontextprotocol/sdk` 1.32.1 and the Python `mcp`

AI ENGINEERINGDECODED.

Medium

What is the Model Context Protocol (MCP) and what problem does it solve?

Tool calling vs function calling vs structured output — what changed in 2025?

How do you design good tool definitions for an LLM?

Hard

How should an agent handle tool errors, timeouts and retries?

MCP authoring: how do you build a Model Context Protocol server in 2025-26?