About llmtools

llmtools is a focused collection of tools for people working with language models. The site brings common planning, formatting and comparison tasks together in one place, with clear explanations of what each tool can and cannot tell you.

What we offer

• Token Counter — Count OpenAI tokens with the model-matched tokenizer and compare them with labelled Anthropic and Gemini estimates.
• LLM Cost Estimator — Project monthly API spend across models from your token volume and request count.
• Model Comparison — Context windows, max output and per-million pricing for current models, sortable and filterable.
• Context Window Visualizer — See how much of a model’s context window your prompt actually uses.
• Prompt Formatter — Turn a conversation into the exact request shape each provider’s API expects.
• JSON Schema Generator — Generate function-calling schemas for OpenAI, Anthropic and Gemini from one definition.
• System Prompt Library — A curated library of system prompts, searchable by category.

Our approach

We aim to make technical decisions easier to understand without overstating certainty. Results can depend on the information and assumptions provided, so important decisions should always be checked against the relevant provider or source.

Privacy and feedback

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