---
title: "Check Domain Limit"
method: POST
path: "/v1/auth/check-domain-limit"
tags: ["domain-limit"]
---

# Check Domain Limit

`POST /v1/auth/check-domain-limit`

## Request

- Base URL: `https://api.pioneer.ai` (the document declares no server; this is the origin it was published from)
- URL: `https://api.pioneer.ai/v1/auth/check-domain-limit`
- Auth: none required
- TypeScript: <https://skmtc.dev/pioneer/apis/brain-api/docs/v1/auth/check-domain-limit/post.ts> (a function with typed inputs; its response is checked against the schema)

Check whether admitting an address would break the domain signup rules.

In order: an excluded domain bans, an included domain admits, an existing
account for the submitted address admits, else members are counted against
SIGNUP_DOMAIN_LIMIT. That third rule makes an over-cap domain answer
whether the address has an account; the IP rate limit is what bounds it.

Args:
    request: Incoming request, required by the rate limiter.
    body: Submitted address, as a full ``email`` or a bare ``domain``.

Returns:
    Whether another signup is allowed, and whether the domain is banned.

Raises:
    HTTPException: 400 if the domain is empty or malformed.

## Request body

- DomainLimitRequest: Address to evaluate against the domain signup rules. One of ``domain`` or ``email`` is required. Prefer ``email``: only it lets the service exclude an account that already exists for that exact address from its own answer.
  - `domain` string, nullable: Bare email domain. Carries no identity, so the submitter is counted against the cap like any new signup.
  - `email` string, email, nullable: Full address being admitted. An account that already exists for this exact address is admitted without counting against the cap.

## Response `200`

Successful Response

- DomainLimitResponse: Response describing whether another signup is allowed for a domain.
  - `allowed` boolean, required
  - `banned` boolean

## Other responses

- `422`: Validation Error

## Changes

- **2026-09-24** `0e5e86e2bae5`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/pioneer/apis/brain-api/changes/v1/auth/check-domain-limit/post.md)

---

[API](https://skmtc.dev/pioneer/apis/brain-api.md) - [All operations](https://skmtc.dev/pioneer/apis/brain-api/llms.txt) - [OpenAPI document](https://skmtc.dev/pioneer/apis/brain-api/revisions/0e5e86e2bae5?raw)