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Check an AI’s proposed refund against the customer’s words

Markus Eisele uses Jev and LangChain4j to check whether an AI’s proposed refund matches the customer’s original request, then compares question designs on English and German examples.

Original by Markus EiseleEvaluation

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Credits

“Jev and LangChain4j: Checking AI Tool Calls in Java” by Markus Eisele. Read the original source.

This expanded guide is an AI-narrated adaptation prepared by JevMade. It expands the source’s essential ideas, examples and caveats in JevMade’s own words and is not a word-for-word reading. The synthetic voice does not imitate the author or imply their endorsement.

Our summary

An AI assistant might propose refunding twelve euros when a customer asked for twelve cents. Markus Eisele shows how Java software can use Jev, a tool that answers set questions, to compare a proposed action with the customer’s original words. Permission checks and amount limits still belong in ordinary code.

LangChain4j connects those questions to Java methods. Jev receives the original request, the exact proposed action and relevant order details. Java then allows, rejects or holds that proposal for review. If its amount, order or action changes, it needs a fresh check; execution must also prevent duplicate payments.

Eisele compares two question designs on 24 English and 24 German cases. Separate checks for the order and amount wrongly approved a German request that explicitly forbade payment. His small exploratory test shows why matching details is not enough: the questions must also establish that the customer wants the action.

Key takeaways

  1. Compare the exact proposed action with the original request, not an assistant’s shortened account of it.
  2. Keep access rights, refund limits and payment execution in code; a high model probability is not permission to pay.
  3. Test incorrect approvals and cases held for review together; splitting a question can lose an important condition.

The LangChain4j examples use experimental September 2026 snapshots. The author’s comparison used direct Java HTTP calls, not the LangChain4j integration, and executed no refunds.

Markus Eisele (@myfear) · Original published

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