# Discovery

To find servers that support a token pair, clients call the `getURLsForToken` function on the [Registry](https://github.com/airswap/airswap-about/blob/master/technology/deployments.md) contract for each token and then intersect the results. For example, if the resulting URLs for token A are `[maker1.com, maker2.com]` and for token B are `[maker2.com, maker3.com]` then the only server supporting swapping token A for B is `maker2.com`.

See `getURLsForToken` on the Registry contract:

```typescript
function getURLsForToken(address token) external view returns (string[] memory urls);
```

Check [deployments](https://github.com/airswap/airswap-about/blob/master/technology/deployments.md) for latest contract addresses for Registry.

## Fetching URLs via CLI

Ensure the AirSwap CLI is installed.

```
$ yarn global add airswap
```

Use `airswap chain` to set your chain to Goerli or Mainnet.

```
$ airswap chain
AirSwap CLI 4.0.1 — https://www.airswap.xyz/

set the active ethereum chain

Current chain: 5 (GOERLI)

New chain id:  (5) 1

Set active chain to ETHEREUM.
```

Use `registry:get` to fetch server URLs for a token pair.

```
$ airswap registry:list
AirSwap CLI 4.0.1 — https://www.airswap.xyz/

get urls from the registry ETHEREUM

Registry 0x8F9DA6d38939411340b19401E8c54Ea1f51B8f95

Token pair (e.g. WETH/USDT):  dai/weth

Server
----------------------------------------
https://maker.example.com/
```

### Example: Take an Order

Try `airswap order` with a server URL from the previous command.

## TypeScript

Using the `Registry` library from `@airswap/libraries` returns `Server` instances that you can interact with.

```typescript
import { ProtocolIds } from '@airswap/utils'
import { Registry } from '@airswap/libraries'
const servers = await Registry.getServers(
  provider,
  chainId,
  ProtocolIds.RequestForQuoteERC20,
  signerToken,
  senderToken,
)
```

Calling the Registry directly using `ethers`

```typescript
import { ethers } from 'ethers'
import { chainNames } from '@airswap/utils'
import * as RegistryContract from '@airswap/registry/build/contracts/Registry.sol/Registry.json'
import * as registryDeploys from '@airswap/registry/deploys.js'
const RegistryInterface = new ethers.utils.Interface(
  JSON.stringify(RegistryContract.abi),
)

new ethers.Contract(
  registryDeploys[chainId],
  RegistryInterface,
  ethers.getDefaultProvider(chainNames[chainId].toLowerCase()),
)

const signerTokenURLs = await this.contract.getURLsForToken(signerToken)
const senderTokenURLs = await this.contract.getURLsForToken(senderToken)

const serverURLs = signerTokenURLs.filter((value) =>
  senderTokenURLs.includes(value),
)
```

### Example: Take an Order

```typescript
import { Registry, SwapERC20 } from '@airswap/libraries'
import { ProtocolIds, chainNames, orderERC20ToParams } from '@airswap/utils'

const servers = await Registry.getServers(
  provider,
  chainId,
  ProtocolIds.RequestForQuoteERC20,
  signerToken,
  senderToken,
)

const order = servers[0].getSignerSideOrderERC20(
  senderAmount,
  signerToken,
  senderToken,
  senderWallet,
)

await SwapERC20.getContract(provider, chainId).swapLight(
  ...orderERC20ToParams(order),
)
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://about.airswap.xyz/technology/discovery.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.