Tool Call Cost Calculator
Estimate the cost of function/tool calling in agents.
With the default inputs, $0.0125 per run — 5 tool calls · ~$375.00/month. Enter your own numbers below to recompute instantly; the full step-by-step math is shown under the worked example.
Results update automatically as you type.
- Tool calls / run
- 5
- Cost per run
- $0.0125
- Cost per month
- $375.00
Every tool call sends context in and gets a result back, plus any external API cost. Estimate the cost per agent run based on how many tools it calls.
How this is calculated
Cost per run = tool calls × (input tokens per call × input price + output tokens per call × output price) + tool calls × external API cost per call. Each tool call round-trips the growing context plus the tool result, so many small calls can cost more than one larger prompt. Monthly = per-run × runs per day × 30.
Is this a good result? What to do next
Tool calls aren't free even when the tool itself is: the schema and results are tokens, and context is resent each round-trip. If tool cost is high, it's usually the number of calls and the size of results, not the model.
Typical planning ranges
- Each call
- input + output tokens + optional external cost
- Many small calls
- can exceed one larger prompt
- Schemas + results
- pure token overhead
Ranges are typical planning figures to sanity-check your result, not authoritative benchmarks. Your numbers will vary with use case, volume, and vendor.
How to improve this number
- Reduce round-trips; batch or parallelize tool calls.
- Trim tool schemas and truncate verbose results.
- Cache the tool block if the provider supports it.
Common mistakes
- Ignoring external API cost per call.
- Verbose tool results inflating every round-trip.
When to use a different approach
For the whole agent run, use the AI agent cost calculator. For always-on tool schema overhead, use the function calling overhead calculator.
Worked example (defaults)
With the default inputs above, here is the result:
- Tool calls / run
- 5
- Cost per run
- $0.0125
- Cost per month
- $375.00
Sources & references
Frequently asked questions
Do tool calls cost extra tokens?+
Yes. Tool schemas add input tokens, and each call round-trips the growing context plus the tool result, so many small calls can cost more than one larger prompt.
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