---
title: "Link two cards"
method: POST
path: "/api/v2/projects/{projectId}/cards/{cardId}/card-links"
tags: ["Cards"]
---

# Link two cards

`POST /api/v2/projects/{projectId}/cards/{cardId}/card-links`

## Request

- Base URL: `https://davinci-app.com`
- URL: `https://davinci-app.com/api/v2/projects/{projectId}/cards/{cardId}/card-links`
- Auth: HTTP bearer

Links two cards in the same project. `dependency_of` reverses the stored
direction and is returned from the opposite card's perspective. Dependency
cycles are rejected. Re-adding an identical link is accepted and may return
an empty JSON object.

## Headers

- `If-Match` string

## Request body

- AddCardLinkRequest
  - `cardId` string, uuid, required
  - `linkType` 'relates_to' | 'depends_on' | 'dependency_of'
  - `expectedHistoryHeadId` string, uuid, nullable: Latest committed card-history row ID; null only before a card has history.

## Response `201`

Card link created, or already present.

- CardLinkResponse: The `link` field is omitted when the identical card link already existed.
  - `link` AgileCardLink
    - `id` string, uuid, required
    - `card_one_id` string, uuid, required
    - `card_two_id` string, uuid, required
    - `link_type` 'relates_to' | 'depends_on', required
    - `created_at` string, date-time, nullable, required
  - `historyHeadId` string, uuid, nullable, required: Latest committed card-history row ID; null only before a card has history.
  - `historyHeadSequence` string, nullable, required: Globally monotonic card-history sequence.

## Other responses

- `400`: Malformed request parameters or body. Agile requests may return `INVALID_PAGINATION` or `INVALID_IDEMPOTENCY_KEY`.
- `401`: No credential was supplied, or the supplied credential is malformed, expired, or revoked. A credential that is present but unusable is never downgraded to an anonymous request.
- `403`: Authenticated but not authorized. Either the acting user lacks the required resource permission, the key's scope ceiling excludes it, or the endpoint rejects this credential type (`CREDENTIAL_NOT_PERMITTED`).
- `404`: The resource does not exist in the parent named by the path, or is hidden from the caller. Absence and privacy denial are deliberately indistinguishable so project, organization, and private-team existence cannot be probed.
- `409`: The supplied `If-Match`, `expectedHistoryHeadId`, or `expectedHistoryHeadIds` no longer matches committed card history. Error code is `CARD_HISTORY_CONFLICT`; `error.details` includes the expected head, current head and sequence, plus recent card activity. No part of the requested card mutation is applied.
- `429`: Request rate exceeded, either globally or for this key.
- `500`: Unexpected server error.

## Changes

- **2026-09-15** (v2) `67c8b8616dbb`: 1 info
  - endpoint added

[Operation history](https://skmtc.dev/celedon-solutions/apis/davinci-public-api/changes/api/v2/projects/:projectId/cards/:cardId/card-links/post.md)

---

[API](https://skmtc.dev/celedon-solutions/apis/davinci-public-api.md) - [All operations](https://skmtc.dev/celedon-solutions/apis/davinci-public-api/llms.txt) - [OpenAPI document](https://skmtc.dev/celedon-solutions/apis/davinci-public-api/revisions/279218ca2e8d?raw)