# Check your key · Elysium API · Femtos

> Answers the name your key is registered under, its tier, billing state and the limits in force.

- Base URL: `https://api.femtos.xyz/v1` (REST) · `wss://api.femtos.xyz/v1/ws` (WebSocket) · MCP: `https://api.femtos.xyz/mcp`
- Auth: `Authorization: Bearer $FEMTOS_KEY`. Free key: https://femtos.xyz/accounts/ (browser), or with
  no browser: `GET https://femtos.xyz/accounts/agent/challenge`, solve its proof of work, then `POST https://femtos.xyz/accounts/agent/signup`
  (https://femtos.xyz/agents.md#agent-onboarding)
- Decimals are exact strings, times Unix milliseconds, addresses lowercase `0x`
- Whole API in one file: https://femtos.xyz/agents.md · OpenAPI: https://api.femtos.xyz/v1/openapi.json · Index: https://femtos.xyz/llms.txt
- Page with live calls: https://femtos.xyz/hypercore/whoami

## Check your key — GET `/v1/whoami`

Answers the name your key is registered under, its tier, billing state and the limits in force.

```bash
curl -H "Authorization: Bearer $FEMTOS_KEY" "https://api.femtos.xyz/v1/whoami"
```

| Field | Type | Meaning |
|---|---|---|
| `key` | string | name of your key |
| `tier` | string \| null | free · builder · pro · scale · enterprise · partner (null: internal key) |
| `billing` | string | ok · exhausted · capped (the last two run at the free row's limits) |
| `limits` | object \| null | {rps, burst, maxConns} in force: REST rate and burst, open WebSockets (null: no limit) |

## Related (Reference)

- [Blocks stream](https://femtos.xyz/elysium/ws-blocks.md): Each new Elysium block header, from our node.
- [Freshness](https://femtos.xyz/elysium/status.md): Head and lag of each layer, measured now.
- [OpenAPI document](https://femtos.xyz/elysium/openapi.md): The OpenAPI 3.1 contract of every REST call, public.

All Elysium endpoints: https://femtos.xyz/elysium.md