Hello World, LangChain

A first LangChain chain, from prompt template to LCEL pipe, with a local model swap, response inspection, tests, type-checking, and tracing added around it.

Tool Calling with LangChain

How create_agent and the @tool decorator collapse a hand-rolled tool-calling loop into a few lines, and what that trade-off actually costs you.

A Minimal Eval Harness

A small, hand-rolled harness for checking whether an agent’s output is actually correct, not just well-formed, with a fixed dataset, a scorer per case, and a pass rate.

LLM-as-Judge

When correctness is subjective, grade agent output with a second, structured LLM call instead of eyeballing every run.