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mcp: apply defaults to null tool arguments - #1343
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guglielmo-san merged 1 commit intoOct 5, 2026
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A tools/call request with "arguments": null for a tool whose input schema declares a default panicked the server: unmarshaling null into the map in applySchema leaves it nil, and ApplyDefaults then writes to it. Treat null arguments like omitted ones. Fixes modelcontextprotocol#1340
guglielmo-san
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Oct 5, 2026
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@pkarpovich thank you for the contribution! |
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A
tools/callrequest with"arguments": nullfor a tool whose input schema declares a default panics the server withassignment to entry in nil map. Unmarshalingnullinto the map inapplySchemaleaves it nil, andApplyDefaultsthen writes into it.This treats null arguments like missing ones, so the defaults are applied and the call proceeds.
The elicitation paths already skip
ApplyDefaultson a nilContent(#1069), soapplySchemais the only place that needed the check.The two new
TestApplySchemacases panic onmain.Fixes #1340