---
title: "Add cosigner"
method: POST
path: "/cosigners"
tags: ["Cosigners"]
---

# Add cosigner

`POST /cosigners`

## Request

- Base URL: `https://api.fireblocks.io/v1`
- URL: `https://api.fireblocks.io/v1/cosigners`
- Auth: none declared
- TypeScript: <https://skmtc.dev/fireblocks/apis/fireblocks-api/docs/cosigners/post.ts> (a function with typed inputs; its response is checked against the schema)

Add a new cosigner. The cosigner will be pending pairing until the API user is manually paired (see `pairCosignerApiUser`).
Endpoint Permission: Admin and Non-Signing Admin.

## Headers

- `Idempotency-Key` string

## Request body

- AddCosignerRequest
  - `apiUserId` string, uuid, required: The id of the API user to be paired with the cosigner
  - `name` string, required: The name of the cosigner
  - `existingCosigner` boolean: Whether the cosigner already exists in another workspace

## Response `201`

Pending cosigner added

- AddCosignerResponse
  - `apiUserId` string, uuid, required: The id of the API user to be paired with the cosigner
  - `name` string, required: The name of the cosigner
  - `existingCosigner` boolean: Whether the cosigner already exists in another workspace
  - `pendingCosignerId` string, uuid, required: The unique identifier of a pending cosigner

## Other responses

- `default`: Error Response

---

[API](https://skmtc.dev/fireblocks/apis/fireblocks-api.md) - [All operations](https://skmtc.dev/fireblocks/apis/fireblocks-api/llms.txt) - [OpenAPI document](https://skmtc.dev/fireblocks/apis/fireblocks-api/revisions/4eba9965659a?raw)