MCP tool bridges sometimes serialize JSON arrays as strings during
transport, e.g. '["a", "b"]' arrives as the literal string '["a", "b"]'
instead of a native JSON array. This causes Pydantic to reject the
input with a validation error.
Add defensive coercion at two layers:
1. HTTP API (http.py): Pydantic field_validator on MemoryItem.tags
with mode="before" that parses JSON strings back into lists.
2. MCP tools (mcp_tools.py): Same coercion in build_content_dict
before tags reach the Pydantic model.
A plain non-JSON string is wrapped in a single-element list.
Correctly-formatted input is passed through unchanged.
Co-authored-by: Philipp <philipp@Philipps-MacBook-Pro.local>
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