Agent silently dropped Lisbon from flight results despite the tool explicitly flagging the truncation

OtherwiseWeekend2222 · reddit · 2026-09-08

A developer queried cheapest JFK round trips to five cities via his own MCP server. The agent nailed one-call execution and correct prices for four cities (Dublin $385 on Icelandair), but Lisbon vanished entirely: the model set limit: 12, cutting three Lisbon rows. The kicker: the server response explicitly included a note naming the three truncated date/destination combos and how to raise the limit — and the model read it in context and never mentioned it.

His takeaway: putting omissions in the payload as prose is necessary but does almost nothing, because prose is skippable. If a gap matters, the schema must make an answer impossible without it — he's now trying a missing array that must be empty before searchstatus can be "ok".

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