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

# Data Structure Indexer API

> Query accumulators, remappers, and proof-support data structures used by Herodotus Storage Proofs and Data Processor APIs.

<img src="https://mintcdn.com/herodotuscloudservices/S302XnSN--WAs0sk/images/banners/data-structure-indexer.webp?fit=max&auto=format&n=S302XnSN--WAs0sk&q=85&s=a498df4b8688bb6c5fd4fc9b66dddb1c" alt="Indexer Banner" width="1199" height="289" data-path="images/banners/data-structure-indexer.webp" />

<Note>
  Have a look at the [Data Structure Indexer API AI Skill](/skills/data-structure-indexer-api)
  to give your LLM a head start on indexer workflows.
</Note>

## Overview

The **Data Structure Indexer API** provides a convenient way to query and verify on-chain data structures—particularly *Merkle Mountain Range (MMR) accumulators* and *remappers* that map timestamps to block numbers. Built on top of these cryptographic accumulators, the API supplies endpoints for retrieving proofs, peaks, and other metadata, allowing developers to validate and explore block data from various chains.

## Key Concepts

### Accumulators

An **accumulator** is a data structure (in this case, a Merkle Mountain Range) used to store and prove the inclusion of block headers. The API:

* **Lists all accumulators** on a given chain (and the chains they reference).
* **Provides Merkle proofs** to confirm block header inclusion in an MMR.
* **Exposes helper data** like the MMR's root hash, size, and peaks.

### Remappers

A **remapper** is another MMR-based construction used for mapping timestamps to block numbers and verifying these relationships. The API includes:

* **Endpoints to fetch the remapper peaks**, which reveal the top-level hashes of the structure.
* **Binary search path retrieval** by timestamp to pinpoint a matching block number.
* **Block-to-timestamp mappings**, enabling cross-chain time-based lookups.