> ## 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 130+ 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.

> Pick the right data sources for Substrate Squid SDK indexers.

# Substrate data sourcing

## How do I know which events and calls I need on Substrate?

This part depends on the runtime business logic of the chain. The primary and the most reliable source of information is thus the Rust sources for the pallets used by the chain.

For a quick lookup of the documentation and the data format, it is often useful to check Runtime section of Subscan (e.g. [Statemine](https://assethub-kusama.subscan.io/runtime)). One can see the deployed pallets and drill down to events and extrinsics from there. One can also choose the spec version on the drop down.


## Related topics

- [Make an indexer](/en/sdk/squid-sdk/substrate/guides/make-an-indexer.md)
- [Block data for Substrate](/en/sdk/squid-sdk/substrate/reference/substrate-processor/context-interfaces.md)
- [Glossary](/en/other/glossary/glossary.md)
- [SQD vs The Graph](/en/sdk/subsquid-vs-thegraph.md)
- [Astar (Substrate)](/en/data/substrate/astar-substrate.md)