# Can Jev choose which tool an agent calls?

Yes: TypeSafe's own function-calling cookbook has Jev answer one choice question, "What is the user asking the trading assistant to do?", with every tool's description from `spec.json` listed alongside the built-in answers, and it returns a confidence with whichever function it picks. That confidence is the call's weakest link, the least certain of the tool choice and every argument together, not a product, because one wrong argument is enough to spoil the result.

The cookbook's own fourteen test commands show the range: a clear request like "what tickers do you have" scored 1.00, while an ambiguous one, "when during the day does nvda trade the most," scored 0.53. [The same threshold pattern used for any Jev decision](/answers/system-one-models/how-do-i-pick-a-confidence-threshold-for-a-decision) applies here: route the low-confidence picks to an LLM or a person instead of calling whatever tool Jev happened to choose.

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Sources:
- TypeSafe docs, Function calling cookbook: https://docs.typesafe.ai/cookbooks/function_calling.md (fetched 2026-09-21)

Source: https://tessary.ai/answers/jev/can-jev-choose-which-tool-an-agent-calls
More on Jev: https://tessary.ai/answers/jev
From Tessary, agent reliability for AI agents in production: https://tessary.ai