[v1.x backport] Use correct schema for client sampling validation when tools are present #1407
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…sent When a sampling request includes tools or toolChoice, the client now validates the response against CreateMessageResultWithToolsSchema (which supports array content with tool_use blocks) instead of always using CreateMessageResultSchema. This fixes validation failures when client handlers return tool_use content formatted as an array, which was incorrectly rejected with "Invalid input: expected object, received array". Fixes modelcontextprotocol#1346 🦉 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Summary
Backport of #1347 to v1.x branch for inclusion in a v1.x.x point release.
Fix client-side sampling validation to use
CreateMessageResultWithToolsSchemawhen tools are present in the request, preventing false validation failures for tool_use responses.Motivation and Context
When a client sampling handler returns
tool_usecontent formatted as an array, validation fails with "Invalid input: expected object, received array". This occurs because the client always validates againstCreateMessageResultSchemaregardless of whether tools were included in the request.CreateMessageResultSchemaexpects single content blocks (text, image, or audio only)CreateMessageResultWithToolsSchemasupports array content with tool_use/tool_result blocksThis mirrors the server-side fix from PR #1156, which the client-side code missed.
Fixes #1346
How Has This Been Tested?
Added 5 new integration tests in
test/client/index.test.ts:[{ type: 'tool_use', ... }]toolChoicealso triggers the correct schemaAll tests pass.
Breaking Changes
None
Types of changes
Checklist
🦉 Generated with Claude Code
Co-Authored-By: Claude Opus 4.5 noreply@anthropic.com