Minimum-first framing: build one tiny custom tool with success and error-path evidence; MCP server wiring remains optional extension.

Day 1 · Block 5

Tools 2

Move from tool user to tool builder by creating and connecting a tiny MCP-style tool.

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Block Write-up

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Exercise overview: Connect LangChain agent to MCP time server

Inputs

• exercises/05/mcp_tool.py
• mcp-server-time via uvx
• LangChain MCP adapters

Deliverable

MCP tool-call evidence (success + error) + sanity check + one TODO change note.

Target

Take a look at https://docs.langchain.com/oss/python/langchain/human-in-the-loop ; when would this be useful in your work?

Submission

• Use the live launcher: Live Exercises
• Direct prefilled form: E05 submission link

Checklist

• Make one explicit design decision.
• Include one verification check.
• State one limitation or risk.

Common failure modes

• uvx/mcp-server-time not available.
• No explicit error-path evidence.

Extension task (optional)

Connect one additional MCP server and run one extra query.