A 200 from a tool call isn't proof your agent did the thing: verify with read-backs
Several-Yellow2713 · reddit · 2026-10-12
A Reddit poster highlights a widespread agent engineering blind spot: a successful tool-call response only means the API accepted the request, not that the action actually happened. Typical failure: the agent claims it sent the proposal, the trace is green — and the email is still in Drafts.
The proposed labeling framework:
- verified: read back the object after writing and it matches the agent's intent
- acknowledged: the API said yes but nothing was read back (all a 200 is worth)
- contradicted: read-back disagrees with what the agent claimed — the bucket that matters, since otherwise you learn about failures from customers
Two companion rules: a failed read-back (network error, missing id) is "unchecked", not "contradicted"; a record that exists but has nothing to compare stays "acknowledged". The practice: fetch the object after every write and compare with intent.
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