refactor: apply MCP argument coercion only as a fallback after validation failure - #9823
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…tion failure Instead of rewriting tool-call arguments on every request before validation, let the SDK validate the original arguments first; only when validation fails with a JSON-RPC invalid-params error, coerce the stringified fields and retry the call once. Calls that validate as-is are never rewritten. Claude-Session: https://claude.ai/code/session_01QQXgoSbvvNyD9877qZ5Wou
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If we are doing it only on failures then it may be okay to get rid of the instance config/feature flag as well IMO. |
With coercion applied only as a fallback after validation failure, it can no longer alter a valid request, so the opt-out is unnecessary. Claude-Session: https://claude.ai/code/session_01QQXgoSbvvNyD9877qZ5Wou
Gives operators a signal for how often the client-side serialization bug occurs, and hence when the workaround can be retired. Claude-Session: https://claude.ai/code/session_01QQXgoSbvvNyD9877qZ5Wou
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Follow-up to #9821, addressing this review suggestion:
tools/call.coerceMCPToolArgsnow reports whether it changed anything, so unchanged arguments skip the retry and return the original validation error.rill.ai.mcp_tolerant_argsconfig option introduced in fix: tolerantly decode stringified JSON object arguments in MCP tool calls #9821 is removed again (including its docs entry and test).Checklist:
https://claude.ai/code/session_01QQXgoSbvvNyD9877qZ5Wou