Tool Schema Diff
Tool schemas change under you. Some of those changes break calls outright; the more awkward ones change nothing structural and simply make the model choose differently. Paste both versions to see which is which.
Output appears here as you type.
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Questions
Is what I paste sent anywhere?
No — and it is worth being concrete about why that matters here. A prompt, a captured response and a tool definition all contain the things people are most careful with: system instructions, customer data, internal endpoints. Every tool on this page is a pure function running in your tab, on a page whose Content-Security-Policy sets connect-src to ‘none’, so the browser will not let it open a network connection at all.
Why is a description change worth flagging?
Because it is the one that gets missed. The signature is unchanged, every existing call still validates, nothing errors — and the model now decides differently about when to reach for the tool and what to put in its arguments. A line diff shows it as one changed string among many; here it gets its own category.
What counts as breaking?
A tool removed, an argument removed, a required argument added, a type changed, an optional argument becoming required, allowed values removed from an enum, or strict mode being switched on. Each of these rejects a call that previously worked.
Why does this need a tool at all?
Because tool sets have no versioning discipline yet. There is no contract testing and no breaking-change detection in the ecosystem, so a server can change what it exposes between deploys with nothing to compare against. A drifted tool does not throw — it returns a confident wrong answer, which is considerably harder to notice.
More inspect tools
Tool definition linter
Check a tool definition against the constraints the API actually enforces.
Streaming response inspector
Reconstruct a message from a raw SSE stream and find where it broke.
Tool schema budget
Find which tool definitions are eating your context, and the fields duplicated across them.