Fix critical issues found during staging QA testing:
1. data parameter serialization: MCP transport sends JSON as strings —
added z.preprocess coercers (coerceJsonArray, coerceJsonObject,
coerceJsonFilter) to parse string→JSON before Zod validation
2. filter/sortBy URL encoding: n8n API requires URL-encoded query params —
added encodeURIComponent() for filter and sortBy in getRows/deleteRows
3. json column type: n8n API only accepts string|number|boolean|date —
removed json from enum in types, Zod schema, tool definition, and docs
4. 404 error messages: N8nNotFoundError was wrapping API messages in
"Resource with ID <message> not found" — now passes through cleanly
5. Unit test expectations updated for URL-encoded filter/sortBy values
Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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