Agents Deployed

Explained series Episode 3 about 11 min

Tools and MCP: how an AI model does anything

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About this episode

How an AI model uses tools when all it can do is write text: what a tool definition is, how tool calling (function calling) really works, what makes a tool easy for a model to use, and MCP, the Model Context Protocol, the standard way to plug tools into any AI app.

Written by Kiran Krishna. Narrated with an AI voice. · LinkedIn

In this episode

  1. 0:01An AI model can't press a single button.
  2. 0:58Here's the plan.
  3. 1:10So what is a tool, to a model?
  4. 2:35So how does the model use one?
  5. 5:43So if the description is all the model goes on, what makes a good one?
  6. 8:00So far, you've written every tool yourself.
  7. 10:30So how does a model that can only write text do anything at all?

Sources check every one

  1. Anthropic, Building effective agents (more time on the tools than the prompt; the full-path fix) anthropic.com
  2. Anthropic, Advanced tool use (the commonest mistakes; 58 tools and about 55,000 tokens from five MCP servers) anthropic.com
  3. Anthropic docs, defining tools (name, description and input schema; tools go into the system prompt; the description matters most; at least 3–4 sentences) platform.claude.com
  4. OpenAI docs, function calling (tools go into the system message; the intern test; fewer than 20 functions; tool search) developers.openai.com
  5. Google, Gemma 4 31B chat template and word list (our counts: a tool adds 95 tokens, a request is 19, descriptions of 4 and 69; the tool tokens) huggingface.co
  6. Anthropic docs, tool use overview (your app runs the call; the model stops at a tool call) platform.claude.com
  7. Anthropic docs, parallel tool use (several requests at once) platform.claude.com
  8. Anthropic docs, handling tool calls (errors that say what went wrong and what to try instead) platform.claude.com
  9. Anthropic, Writing effective tools for agents (describe it as you would to a new hire; a few clear tools, not one per API call) anthropic.com
  10. Google, Gemini API function calling docs (the model doesn't run the function itself; 10–20 tools at most) aistudio.google.com
  11. Anthropic docs, tool search (letting the model search for its tools) platform.claude.com
  12. Hugging Face MCP course (M×N connections become M+N; our 12 vs 7) huggingface.co
  13. Anthropic, MCP launch post (an open standard, 25 November 2024) anthropic.com
  14. MCP docs, introduction (the USB-C port comparison) modelcontextprotocol.io
  15. MCP docs, architecture (clients and servers; listing and calling tools; resources and prompts) modelcontextprotocol.io
  16. TechCrunch, OpenAI adds MCP to its Agents SDK (26 March 2025) techcrunch.com
  17. Anthropic, donating MCP to the Agentic AI Foundation (ChatGPT, Gemini, Microsoft Copilot and VS Code support, December 2025) anthropic.com
  18. Linux Foundation, the Agentic AI Foundation's launch (set up with Anthropic, OpenAI and Block, December 2025) linuxfoundation.org
  19. Linux Foundation, September 2026 (MCP's software kits approaching half a billion downloads a month) linuxfoundation.org