# Holdstack

> Holdstack is an API for European UCITS ETF data: holdings, look-through and exposures, normalized from the issuers' own
> published documents. Status: pre-launch (validation). The interface below is planned and may change before launch.

## What it will provide

- Holdings of any UCITS ETF by ISIN: constituents with weight, shares, value, sector and country, plus the data date.
- Fund details: issuer, index, domicile, replication, distribution, currency, TER, AUM, number of holdings.
- Look-through: send a portfolio of ETFs and stocks, get the combined exposure by holding, country, sector and currency.
- Overlap between ETFs, and "held by": which ETFs own a given stock and at what weight.
- Alerts by webhook when holdings change, the TER moves or a new ETF lists.
- Provenance: every field links to its source document and date.

## Planned endpoints

- `GET https://api.holdstack.io/v1/etf/{isin}/holdings`
- `POST https://api.holdstack.io/v1/look-through` with `{"positions":[{"isin":"...","value":10000}]}`
- `GET https://api.holdstack.io/v1/stock/{isin}/held-by`

Authentication: `Authorization: Bearer <key>`. An MCP server (`holdstack-mcp`) is planned for AI agents.

## Contact and early access

- Site: https://holdstack.io/
- Email: hello@holdstack.io