Context engineering
Assemble the smallest, clearest set of instructions, evidence, examples, and tool results needed for a task.
- 11 minutes
- intermediate
- Reviewed 2026-07-16
What is it?
Context engineering designs everything a model sees: system instructions, user input, examples, retrieved sources, prior state, and tool results.
Why does it matter?
More text can hide the important signal, create conflicts, increase cost, and push useful evidence outside the context limit.
The mental model
Context is the model's working desk. Put only relevant, trustworthy material on it and label every piece.
A simple example
A support assistant receives one policy section, the current order record, and a required response format—not the entire company drive.
What it is not
It is not prompt decoration or a race to create the longest system message.
Learn this first
These ideas make the lesson easier to place.
- Model selection
- Prompts
Your first 60 minutes
Use one focused hour to make the idea concrete.
- List every information source for one task.
- Remove anything that cannot change the answer.
- Label instructions, evidence, and untrusted user content separately.
Build this first
Create two context packages for the same question and compare which produces more grounded, concise answers.
When not to use it
Do not send confidential or irrelevant data merely because a model can accept a large context window.
What to learn next
Learn retrieval, grounding, and tracing.