Choosing an LLM and AI stack

Sefism.

A to Z

Glossary

Every concept in this sheet, plus the smaller terms it uses. Select a concept to open its card.

B
Benchmarks
Fixed public test sets with a published score per model, for coding, maths, knowledge and agent tasks.
C
Compounding errors
In a task with many steps, per-step accuracy multiplies: 95% per step over 10 steps is about 60% overall.
D
Dated snapshots
Every table of model names, prices or context windows is a photograph of one day.
E
Effort and thinking settings
A request setting that controls how much a model reasons: Anthropic calls it effort, OpenAI reasoning effort, Gemini a thinking setting.
I
Instruction following
How faithfully a model obeys your format, length, language, tone and must-not rules, including many turns into a conversation.
L
Leaderboards
Public rankings of models.
M
Model requirements card
Six lines written before any testing: quality (and the cost of a wrong answer), speed, volume, context size, tools and privacy.
Model tiers
Providers sell a family in sizes: a top tier (most capable, slowest), a middle workhorse and a small, cheap, fast tier.
P
Price plus cost of errors
Total cost per request = model price + (error rate x cost of one wrong answer).
R
Reasoning model
A model that writes hidden working before its final answer.
Reasoning tokens
The tokens a model spends thinking before its visible answer.
T
Task families
Five common kinds of LLM work: chat, coding, research, data analysis and workflow automation.
The cheapest model that is good enough
The model to ship is the cheapest and fastest one that clears your quality bar for this task, not the smartest one available.
W
Which model for which job
A starting point for each kind of job: which tier to test first and when to step up or down.
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