---
title: "Signal beacon node to prepare for a committee subnet"
method: POST
path: "/eth/v1/validator/beacon_committee_subscriptions"
tags: ["ValidatorRequiredApi", "Validator"]
---

# Signal beacon node to prepare for a committee subnet

`POST /eth/v1/validator/beacon_committee_subscriptions`

## Request

- Base URL: `eth2-beacon-mainnet.nodereal.io/v1/api_key` (relative, and the document’s source URL is not known)
- URL: `eth2-beacon-mainnet.nodereal.io/v1/api_key/eth/v1/validator/beacon_committee_subscriptions`
- Auth: none declared

After beacon node receives this request,
search using discv5 for peers related to this subnet
and replace current peers with those ones if necessary
If validator `is_aggregator`, beacon node must:
- announce subnet topic subscription on gossipsub
- aggregate attestations received on that subnet

## Request body

- object[]
  - `validator_index` string
  - `committee_index` string
  - `committees_at_slot` string: Number of committees at the returned slot
  - `slot` string: Should be slot at which validator is assigned to attest
  - `is_aggregator` boolean: Signals to BN that a validator on the VC has been chosen for aggregator role.

## Response `200`

Slot signature is valid and beacon node has prepared the attestation subnet.

Note that we cannot be certain the Beacon node will find peers for that subnet for various reasons.

## Other responses

- `400`: Invalid request syntax.
- `500`: Beacon node internal error.
- `503`: Beacon node is currently syncing, try again later.

---

[API](https://skmtc.dev/nodereal/apis/eth-beacon-node-api.md) - [All operations](https://skmtc.dev/nodereal/apis/eth-beacon-node-api/llms.txt) - [OpenAPI document](https://skmtc.dev/nodereal/apis/eth-beacon-node-api/revisions/1878ea8657a1?raw)