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Prompting & Structure

Instruction Following

The model’s ability to actually obey what you asked.

Definition

How faithfully a model respects explicit constraints — format, length, prohibitions, ordering. It degrades as instructions accumulate or conflict.

Every added instruction competes with the others. Past a handful of hard constraints, models start dropping some. Keep the must-haves few, explicit and near the end.

Treat constraints as a budget. Each hard requirement competes with the others, and past a handful, the model silently chooses which to honour. The discipline is to keep must-haves few, explicit and near the end, and to verify them with tests rather than assuming compliance.

How people use it
A prompt with eighteen rules behaving erratically.
"Rank them. The model will follow eight constraints reliably; at eighteen it picks which to forget."
Worked examples

The forgotten constraint

A prompt with eighteen rules reliably drops two of them, and not the same two.

Move the two that actually matter into a post-processing check rather than trusting the prompt, and compress the rest. Deterministic validation on the output is the honest way to enforce a hard constraint; a sentence in the prompt is a request.

Conflict detection

Instructions say both "be thorough" and "keep it under a page".

The model resolves the conflict differently across runs, which looks like flakiness. Resolving it explicitly — depth in the analysis, brevity in the summary — turns an ambiguous instruction into a specific one and the variance drops.

Sources
Related terms