fix: improve Zod v4 optional schema detection#1232
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seongwon030 wants to merge 1 commit intomodelcontextprotocol:mainfrom
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fix: improve Zod v4 optional schema detection#1232seongwon030 wants to merge 1 commit intomodelcontextprotocol:mainfrom
seongwon030 wants to merge 1 commit intomodelcontextprotocol:mainfrom
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- Prioritize `isOptional()` method check in isSchemaOptional to support both Zod v3 and v4 consistently. - Add `typeName` check for Zod v4 internal definitions to correctly identify optional schemas. - Fixes an issue where optional tool arguments were incorrectly marked as required in the generated JSON schema.
commit: |
Contributor
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do you have a repro of this issue? All tests were passing before and it doesnt look like you changed any |
Author
Thanks for the review! After investigating, I found that PR #1199 already fixed this issue. |
Contributor
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Closing this. In any case, thanks for your effort to raise it anyway |
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Motivation and Context
This PR fixes a compatibility issue with Zod v4 where optional schemas were incorrectly identified as required.
Specifically, isSchemaOptional in zod-compat.ts was failing to detect optional fields because it relied on internal properties that differ in Zod v4, causing optional tool arguments to be marked as
requiredin the generated JSON Schema.How Has This Been Tested?
I verified the fix by running the existing test suite (
npm test), specifically theshould support optional prompt argumentstest case in src/server/mcp.test.ts, which now passes correctly.I also manually verified that isSchemaOptional correctly returns
trueforz.string().optional()using Zod v4.Breaking Changes
None. This is a bug fix that improves compatibility.
Types of changes
Checklist