---
title: "Create a relationship instance"
method: POST
path: "/v1/records/{record_id}/relationships"
tags: ["Relationships"]
---

# Create a relationship instance

`POST /v1/records/{record_id}/relationships`

## Request

- Base URL: `https://app.nex.ai/api/developers`
- URL: `https://app.nex.ai/api/developers/v1/records/{record_id}/relationships`
- Auth: API key in header `Authorization`

Creates a relationship instance between two records

## Path parameters

- `record_id` integer, required

## Request body

- DeveloperCreateRelationshipRequest
  - `definition_id` string, required: Relationship definition ID
  - `entity_1_id` string, required: First record ID
  - `entity_2_id` string, required: Second record ID

## Response `200`

Created relationship instance

- DeveloperRelationshipInstanceResponse
  - `id` string
  - `definition_id` string
  - `entity_1_id` string
  - `entity_2_id` string
  - `created_at` string, date-time

## Other responses

- `400`: Bad request - Invalid data
- `401`: Unauthorized - Invalid or missing API key
- `404`: Record not found
- `500`: Internal server error

## Changes

- **2026-02-17** `b05d8cb8cf43`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/nex/apis/nex-developer-api/changes/v1/records/:record_id/relationships/post.md)

---

[API](https://skmtc.dev/nex/apis/nex-developer-api.md) - [All operations](https://skmtc.dev/nex/apis/nex-developer-api/llms.txt) - [OpenAPI document](https://skmtc.dev/nex/apis/nex-developer-api/revisions/51003af13108?raw)