> For the complete documentation index, see [llms.txt](https://doc.duaer.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://doc.duaer.com/getting-started/ligands.md).

# Search ligands in Duaer

In Duaer, look up PDBe chemical component (CCD) ligands with Duaer Data. One successful search uses 1 credit. This page includes the full English call skill.
## What you get

Ligands in the Duaer data market returns PDBe chemical component dictionary rows (name, formula, InChIKey). One successful search uses 1 credit.

Add the node from the [Duaer Data category](/getting-started/duaer-data.md) (Ligands), or copy the skill on the [data market](/getting-started/data-market.md). Related: [Structures](/getting-started/structures.md) and [Compounds](/getting-started/compounds.md).

## Search on the canvas

1. Open the node creator, select Duaer Data, then Ligands.
2. Enter Words or CCD ID (a new node starts with ATP). Comma-separate several ids.
3. Limit defaults to 10, max 20. Select Execute step.

A successful search uses 1 credit. Production deliverables land in the [data pool](/getting-started/data-pool.md).

## Call the API

- GET https://api.duaer.com/v1/data/ligands?...
- Authorization: Bearer <Duaer key>
- words or id (CCD, 1–3 characters) is required.

For keys, refer to [Authentication for the Duaer public API](/api/authentication.md). Below is the same English call skill as Copy skill.

## Call skill

Same text as Copy skill on the Duaer data market. Keep it English.

```
---
name: duaer-ligands
description: >-
  Look up PDBe chemical component (CCD) ligands through Duaer.
  One successful search uses 1 Duaer credit.
---

# Duaer ligands

Look up PDBe chemical component (CCD) ligands through Duaer with a Duaer key.

## Call

`GET https://api.duaer.com/v1/data/ligands?words=ATP&limit=10`

Header: `Authorization: Bearer <Duaer key>`

Use an account key or a model API key.

Provide `words` or `id` as a CCD chemical component id (1–3 characters). Comma-separate several ids.

- `words` — CCD id such as ATP or HEM.
- `id` — optional. Same as words; combine for a batch.
- `limit` — optional. From 1 to 20. Default 10.

## Result

Each item has `source`, `title`, `url`, `summary`, `ccdId`, `name`, `formula`, `weight`, `inchiKey`, `inchi`, `compoundType`, and `firstObservedIn`.
Related structures: https://skills.duaer.com/structures.md.
Related compounds: https://skills.duaer.com/compounds.md.

## Credits

One successful search uses 1 credit.
An empty search, a failed search, a compound that matches nothing, or no remaining credits uses 0.
No remaining credits returns 402 and does not search.
A missing key returns 401.

```
## Questions

### How do Duaer ligands differ from structures?

Ligands look up CCD chemical component definitions. Structures search PDB entries and can filter by a bound ligand name.

## Related

- [Search protein structures in Duaer](https://doc.duaer.com/getting-started/structures.md)
- [Search compounds in Duaer](https://doc.duaer.com/getting-started/compounds.md)
- [Search crossrefs in Duaer](https://doc.duaer.com/getting-started/crossrefs.md)
- [Use the Duaer data market](https://doc.duaer.com/getting-started/data-market.md)