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[Server] Pass an explicit null to a nullable tool parameter with a default - #642
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October 30, 2026 20:15
…fault Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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ReferenceHandler::prepareArguments() now passes an explicit null through to a nullable parameter. Before, isset() treated it as a missing argument, addressing issue #640
Motivation and Context
prepareArguments() tested isset($arguments[$paramName]), so an argument the client sent as null looked missing. A parameter such as ?string $category = 'books' received 'books' instead of null. The schema allows null and the client sent it, but the handler ran with a different value. The check now also accepts a key that is present with a null value when the parameter allows null.
How Has This Been Tested?
I added a unit test, testHandlePassesAnExplicitNullToANullableParameterWithADefault. It checks that an explicit null gives NULL and that an omitted argument still gives the default 'books'.
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