Applications
AI agent run cost estimator
Cost of an agent loop where each step re-reads the growing transcript: steps, tool results and output per step.
Prices read from the vendor pages on 2026-10-20. Arithmetic on list prices, not advice or a quote.
Saving and exports need Norwell Tools Pro, $9 a month. See what is in it. Everything above is free.
How it works
Agents are chatbots that talk to tools: the transcript grows every step and is re-sent every step, so cost is quadratic in step count. Caching the transcript and keeping tool results short are the two biggest savings.
The formula
step n input = system + (n - 1) * (tool_result + output); everything but the newest tool result is cacheable; output per step is billed as outputWorked example
With the inputs the page opens on:
- steps per run: 12
- system and tools tokens: 4000 tokens
- tool result tokens per step: 1500 tokens
- output tokens per step: 300 tokens
- model: claude-sonnet-5-5
- cache transcript: true
- runs per month: 3000
gives
- cost per run: $0.0916
- monthly cost: $274.89
- input tokens per run: 166,800 tokens
- final context tokens: 23,800 tokens
Sources
- https://developers.openai.com/api/docs/pricing (read 2026-10-20)
- https://platform.claude.com/docs/en/about-claude/pricing (read 2026-10-20)
- https://ai.google.dev/gemini-api/docs/pricing (read 2026-10-20)
Prices read from each vendor's own pricing page on 2026-10-20; the page may have changed since. This is arithmetic on published list prices, not advice or a quote. Check the vendor's page before committing a budget.
Questions
What about parallel tool calls?
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