The SIE drop card kept flapping into Claude.ai's Interactive-tools list
and vanishing, and the agent could never call it: every hypothesis
(scope filter, tool-count cap, stale cache, schema shape) was
eliminated against live data until one discriminator remained: all
surviving widget tools carry readOnlyHint true and
gnubok_create_sie_upload was the only one annotated as a write.
Claude.ai accepts always-render widgets only on read-only tools and
silently drops the tool otherwise.
readOnlyHint is now true, which is also honest: the tool only mints a
short-lived upload URL; the actual write is the staged
gnubok_import_sie: the exact receipt_matcher shape (read-only widget
tool, writes via separate approval-gated tools). A guard test pins the
invariant for every future widget tool.
Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
