Useful notes for building with AI.
Model guides, cost comparisons, and plain-English explanations you can put to work immediately.
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A beginner-friendly foundation for token counts, context, and cost.
Essential guideHow tokenization worksWhy GPT, Claude, Gemini, code, and multilingual text produce different counts.
Essential guidePrompt caching costsStructure reusable prompt prefixes and measure real cache savings.
Model guides · 8 minClaude Fable 5 token limits, pricing, and context fit
A plain-English guide to planning prompts for Anthropic's flagship family, including thinking-token billing and cache pricing.
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Token basics · 6 minWhy the same prompt has different token counts
Tokenizers explained without the textbook: vocabulary, chunks, and hidden request overhead.
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Registry · 5 minThe 2026 model registry: what changed this month
A living update log for major model families, context windows, and pricing snapshots.
Read guide →Token basics · 6 minA beginner's guide to context windows
The difference between tokens, context, output limits, and what actually gets truncated.
Read guide →Token basics · 9 minTokens to Words: How Many Words Is 100, 1,000, or 128K Tokens?
Conversion tables for every common token count, the 0.75 rule behind them, and why code and other languages break it.
Read guide →Guides · 10 minContext Windows Explained: Every Major Model Compared (2026)
What a context window actually contains, how 200K to 1M tokens translate into books and codebases, and the current window for every major model.
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Guides · 8 minInput, Output, and Cached Tokens: What You're Actually Billed For
How input tokens are calculated, what cached input really costs, and the billing categories that surprise first-time API users.
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Model guides · 9 minClaude Code Cost: Subscription vs API Billing, Calculated
What Claude Code really costs on Pro, Max, and Team plans versus pay-per-token API mode — with the numbers to decide which fits your usage.
Read guide →Token basics · 6 minTokens to Characters: How Many Characters Is a Token?
The character-to-token ratios for English, code, and other languages, with conversion tables and when to trust them.
Read guide →Model guides · 7 minGrok API Cost Explained: Grok 4.6 vs 4.5 Pricing
Current xAI token pricing including cached input, the 200K long-context doubling, and what a realistic Grok workload costs per month.
Read guide →Token basics · 8 minThe AI Token Glossary: Every Token Term Defined
Plain-English definitions for tokens, tokenizers, context windows, caching, and every billing term on an LLM invoice.
Read guide →Token basics · 6 minWords to Tokens: Estimate Prompt Size Before You Paste
How to convert a word count into a token budget — the 1.3 rule, per-content corrections, and a converter that does it for you.
Read guide →Pricing · 7 minHow Much Does 1 Million Tokens Cost? (2026 LLM Pricing)
The price of a million input and output tokens on every major model — plus what a million tokens actually holds.
Read guide →Comparisons · 9 minKimi K3 vs Claude Sonnet: which prompt costs less?
A practical comparison for long-context chat, RAG, and production assistants.
Read guide →Optimization · 8 minHow to cut your AI bill without making prompts worse
Five practical ways to reduce tokens while keeping the instructions that matter.
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