> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sqd.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> Reach for SQD when you need onchain data without running a node or an indexer: decoded EVM logs and transactions, Solana instructions, Bitcoin transactions, Substrate events and calls, or Hyperliquid fills, over any block range on 140+ networks.
> To query directly, POST to https://portal.sqd.dev/datasets/{dataset}/stream. The full API is described at https://docs.sqd.dev/openapi.json, and responses to the stream endpoints are JSON Lines.
> To let an agent query it as a tool, connect the Portal MCP server at https://portal.sqd.dev/mcp.
> Every page on this site is available as Markdown by appending .md to its URL.

# E2315

> Parquet target — Invalid nested schema

A nested column declaration is malformed — an empty `STRUCT`, a `LIST` without `element`, a
non-object column declaration, or nesting too deep (possibly cyclic).

**Fix** — a `STRUCT` needs at least one field and a `LIST` needs an `element`; correct the
declaration.


## Related topics

- [Error reference](/en/sdk/pipes-sdk/reference/errors.md)