Question 1

AI SDK 5: when to use streamText vs generateText vs generateObject?

Accepted Answer

**Target Audience:** TypeScript developers starting with the Vercel AI SDK who want a clear rule for which core function to call.
**Difficulty:** Easy
**Verified with:** Node 22.22.0 and Python 3.12.3 for the simulation below (identical output). AI SDK facts were read in October 2026 from the published packages on npm: `ai@5.0.277` (latest 5.x) type definitions and source, and the migration guides shipped inside `ai@7.0.143`; release dates are from the npm registry.

> **How to read this doc:**

Question 2

How do you design human-in-the-loop approval for agent actions?

Accepted Answer

**Target Audience:** Engineers adding approval steps to agents that can spend money, message people or change data, and candidates asked to design that step.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (both examples, identical output). Framework APIs were checked in October 2026: AI SDK `ai` 7.0.143 type definitions (read from the published package), the LangGraph and OpenAI Agents SDK docs (via web search), and the `@modelcontextprotocol/server` 2.3.1 doc comments.

Question 3

What is context engineering and how does it differ from prompt engineering?

Accepted Answer

**Target Audience:** Engineers moving from single prompts to RAG systems and agents, who need to explain what changes when "the prompt" becomes a pipeline.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (a context assembler run over simulated candidate items with given token counts; no real model is called). Origins of the term and published guidance are cited inline, checked October 2026.

> **How to read this doc:** Every idea is explained in plain language first, the

Question 4

What is an AI agent and how does the agent loop work?

Accepted Answer

**Target Audience:** Engineers who have called an LLM API and now need to build, or explain, something that takes several steps on its own.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (the example below, identical output). The tool-calling message shapes were checked in October 2026 against the Anthropic docs page "Handle tool calls" (platform.claude.com) and the OpenAI Agents SDK reference for `Runner.run`.

> **How to read this doc:** Every idea is explained in pla

Question 5

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 6

What is hybrid search and why combine BM25 with vector search?

Accepted Answer

**Target Audience:** Engineers whose embedding-only RAG search misses exact terms, and anyone who needs to explain lexical vs semantic retrieval and why teams combine them.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (BM25 written from scratch, a deterministic stub embedding, and RRF fusion on an eight-article knowledge base; no model or search engine is called). Engine facts were checked in each vendor's documentation in October 2026.

> **How to read this doc:** Ev

Question 7

How does function calling (tool use) work under the hood?

Accepted Answer

**Target Audience:** Engineers who have passed a `tools` array to an LLM API and want to know exactly what happens between "the model decided to call a tool" and "the answer came back".
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (a full tool-use loop with a stub model that reads and writes plain text). API behaviour is quoted from the Claude docs ("Define tools", "Handle tool calls", "Stop reasons"), checked October 2026, and other vendors where cited.

> **How to r

Question 8

What is the ReAct pattern and why did it become the default for agents?

Accepted Answer

**Target Audience:** Engineers who know what an agent loop is and want to understand the pattern most agent frameworks are built on, including its history and what is still true today.
**Difficulty:** Medium
**Verified with:** Node 22.22.0 and Python 3.12.3 (the example below, identical output). Paper details were checked in October 2026 against the arXiv listing (2210.03629), the ICLR 2023 proceedings listing and the Google Research blog post on ReAct (November 2022).

> **How to read this doc:

Question 9

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 10

How do you sandbox an agent and enforce least-privilege tool access?

Accepted Answer

**Target Audience:** Engineers giving agents real tools (shell, files, network, API tokens) and candidates facing the "how do you keep an agent safe" question.
**Difficulty:** Hard
**Verified with:** Node 22.22.0 and Python 3.12.3 (both examples, identical output). Vendor references (Claude Code sandboxing docs, MCP SDK source comments, Simon Willison on the lethal trifecta) were checked by web search or by reading the published packages in October 2026.

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

AI ENGINEERINGDECODED.

Easy

AI SDK 5: when to use streamText vs generateText vs generateObject?

Medium

How do you design human-in-the-loop approval for agent actions?

What is context engineering and how does it differ from prompt engineering?

What is an AI agent and how does the agent loop work?

How do you design good tool definitions for an LLM?

What is hybrid search and why combine BM25 with vector search?

How does function calling (tool use) work under the hood?

What is the ReAct pattern and why did it become the default for agents?

Hard

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

How do you sandbox an agent and enforce least-privilege tool access?

When should you split work across multiple agents instead of one?

How would you design a production RAG pipeline end-to-end in 2025-26?

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

What is prompt injection and how do you defend against it?

Guardrails for AI agents: rate limits, budget caps, and HITL?

How do agents maintain memory across steps and sessions?