MCP, agents, tools — explain one to your grandma in two minutes

My grandma is 84 years old. She uses a phone, but only for calls. She does not understand computers. Yesterday, my son asked me a question. What is MCP? I said, let me practice with grandma first. I told her: Grandma, imagine you have one good cook in the family. She can cook many dishes. But she only knows your family fridge. One day, the neighbors want her to cook for them too. But their fridge is different. Their ingredients are different. The cook does not know them. MCP is like a small note. The neighbor writes the note. It says: here is my fridge, here is my stove, here is how I like my eggs. The cook reads the note. Now she can cook at any house. My grandma was quiet. Then she said: so MCP is a note for the cook. I said yes. She said: why do they give it a big name? I did not have a good answer. She said: when you were small, I wrote notes for you too. On the fridge. About the milk, about the medicine. Same idea. I laughed. She was right. MCP is just a note. A note that lets a smart helper work anywhere. If my grandma can understand it, you can too.

我阿嬤八十四歲了。她會用手機，但只用來接電話。她不懂電腦。昨天，我兒子問我一個問題：MCP 是什麼？我說，讓我先跟阿嬤練習一下。 我跟阿嬤說：阿嬤，想像家裡有一個很會煮飯的人。她很多菜都會煮。但是她只熟我們家的冰箱。 有一天，鄰居也想請她煮。可是鄰居家的冰箱不一樣。材料也不一樣。這個很會煮飯的人不熟。 MCP 就像一張小紙條。鄰居寫這張紙條。上面寫：這是我家的冰箱、我家的爐子、我們家蛋要怎麼煎。這個很會煮飯的人看過紙條，就可以去任何一家煮飯了。 阿嬤安靜了一下。然後說：所以 MCP 就是一張給煮飯的人看的紙條。我說對。 她說：那為什麼要取這麼大的名字？我也答不出來。 她說：你小時候，我也在冰箱上貼紙條給你。關於牛奶、關於藥。一樣的意思。 我笑了。她說得對。MCP 就是一張紙條。一張讓聰明的幫手到處都能做事的紙條。 如果我阿嬤聽得懂，你一定也可以。

You've probably heard the acronyms. MCP. Agents. Tools. The tech world loves to name things. But if you can't explain an idea to your grandmother, you probably don't understand it yourself. So here's my attempt, using the grandma-test. Imagine my grandma has one very talented grandchild — call her Claire. Claire can do many things: write letters, plan trips, settle family arguments. But Claire lives in grandma's kitchen. She only knows grandma's recipes, grandma's neighbors, grandma's fridge. She is smart but bounded. Now imagine grandma's friend wants Claire to help at her house too. But her kitchen is different. Different fridge. Different tools. Different habits. Claire doesn't know any of it. MCP is the small instruction sheet grandma's friend writes for Claire. It says: here is my fridge, here is my stove, here is how my family takes their tea. Claire reads the sheet, and suddenly she can help at any house, not just grandma's. Agents are the version of Claire that can do a whole job, not just one step — she plans, she does, she checks, she reports back. Tools are the individual helpers Claire uses, like a calculator or a calendar. Here's the thing. My grandma understood this in one minute. Then she said, "When you were small, I wrote notes on the fridge for you too. About the milk, about the medicine. Same idea." And she was exactly right. MCP is a note. Agents are a competent grandchild. Tools are the things the grandchild picks up. The tech industry will keep giving these ideas big names. Don't be impressed. The good ideas were always simple enough for your grandmother. The bad ones weren't.

你大概都聽過那些縮寫：MCP、Agent、Tools。科技圈很愛幫東西取名字。可是如果你沒辦法把一個觀念講給你阿嬤聽得懂，你大概自己也不是真的懂。所以我來試試看，用阿嬤測試。 想像我阿嬤有一個很厲害的孫女——我們叫她 Claire。Claire 很多事情都會：寫信、安排行程、處理家裡的口角。但 Claire 住在阿嬤家廚房。她只熟阿嬤的食譜、阿嬤的鄰居、阿嬤的冰箱。她聰明，但有疆界。 現在想像阿嬤的朋友也想請 Claire 去她家幫忙。可是她家的廚房不一樣。冰箱不一樣、工具不一樣、習慣不一樣。Claire 一個都不熟。 MCP 就是阿嬤的朋友寫給 Claire 的那張小小的使用說明。上面寫：這是我的冰箱、這是我的爐子、我們家的茶要怎麼泡。Claire 看過這張紙，就可以到任何一家幫忙，不只阿嬤家。 Agent 是那個可以把整件事從頭做到尾的 Claire——她會規劃、會做事、會檢查、會回報。Tools 是 Claire 手上會拿起來的各種小工具，像計算機、日曆。 重點來了。我阿嬤一分鐘就懂了。然後她說：你小時候，我也在冰箱上貼過紙條給你。關於牛奶、關於藥。一樣的意思。她完全說中了。 MCP 是一張紙條。Agent 是一個有能力的孫女。Tools 是她會拿起來用的那些小東西。科技圈會繼續幫這些東西取大名字。不用太崇拜。好的想法，從來都簡單到可以講給阿嬤聽。壞的想法，才需要那個大名字撐著。

If you can't explain a technology to your grandmother in two minutes, you probably don't understand it yet. That was my father's rule, and it has survived every hype cycle I've lived through. So let me try it on the three words currently dominating my field — MCP, agents, and tools — and we'll see whether I understand them or merely use them confidently. Imagine my grandmother has a remarkably capable grandchild — let's call her Claire. Claire is intelligent, patient, and can do many things: draft a letter, plan a birthday dinner, negotiate with the plumber. But Claire, by default, lives in grandmother's kitchen. She knows grandmother's recipes, grandmother's neighbors, grandmother's fridge. She is smart but boundaried, capable but parochial. The question the technology is trying to solve is: how does Claire become useful at every house, not just this one? MCP — the Model Context Protocol — is, at its heart, the small instruction sheet each house writes for Claire. It describes that house's fridge, stove, and family preferences in a shape Claire can read. Once Claire can read these sheets, she can work anywhere. It's a standard, in the way that electrical plugs are a standard. Unglamorous. Transformative. Agents are the version of Claire that can execute an entire errand autonomously — she plans the trip to the market, decides what to buy, handles a price negotiation, and comes home with the dinner. She is no longer a single-turn helper but a multi-step partner. Tools are the individual instruments Claire picks up along the way — the calculator, the calendar, the map. She uses them; they don't replace her. My grandmother, when I tried this explanation on her, paused for a moment and then said: "When you were a child, I used to leave notes on the fridge for you. About the milk, about the medicine. The shape of a helpful note hasn't changed. Only who reads it." She was, as grandmothers tend to be, correct. The good ideas in technology were always simple enough to explain at the kitchen table. The bad ones never were.

一個技術，如果你沒辦法用兩分鐘講給你阿嬤聽懂，你大概還沒真的懂它。這是我爸的規則，在我經歷過的每一次科技炒作潮裡，它都還活著。所以我拿現在最流行的三個字——MCP、agent、tools——來試試看，順便看看我到底是真懂，還是只是用得很熟。 想像我阿嬤有一個能力驚人的孫女——叫她 Claire 好了。Claire 聰明、耐心，很多事都會：寫信、安排生日晚餐、跟水電工議價。可是 Claire 預設住在阿嬤家的廚房。她熟的是阿嬤的食譜、阿嬤的鄰居、阿嬤的冰箱。她聰明，但有疆界；有能力，但地方性。這個技術想解決的問題，其實只有一句：Claire 要怎麼樣才能在每一家都有用，而不只在這一家？ MCP——Model Context Protocol——本質上，就是每一家寫給 Claire 的那一張使用說明。它用 Claire 能讀懂的格式，描述這一家的冰箱、爐子、家庭偏好。一旦 Claire 會讀這些說明，她到哪一家都能工作。它是一個標準，跟電器插頭是標準的意義一樣。不浪漫。但會改變一切。 Agent 是那個可以自己把一整趟差事從頭做到尾的 Claire 版本——她去規劃去菜市場的路線、決定要買什麼、處理殺價、把晚餐帶回家。她不再只是一個回一句話就沒了的幫手，而是一個多步驟的夥伴。Tools 則是她沿路會撿起來用的個別工具——計算機、日曆、地圖。她用它們，不是它們取代她。 我阿嬤聽完之後，停了一下，然後說：你小時候，我也會在冰箱上貼紙條給你。關於牛奶、關於藥。一張會幫忙的紙條長什麼樣子，其實沒有變。變的，只是誰來讀。她說得，像阿嬤們通常那樣，正確。科技裡真正好的想法，一直都可以在廚房的餐桌上講清楚。不好的那些——從來都不行。