> ## Documentation Index
> Fetch the complete documentation index at: https://developer.lemlist.com/llms.txt
> Use this file to discover all available pages before exploring further.

> Adds existing CRM contacts to a static contact list.

# Add Contacts to List

Adds existing contacts to a static contact list. Contacts already in the list are silently skipped — no duplicates are created.

<Warning>
  You cannot add contacts to a **dynamic** list. Dynamic lists are auto-populated based on filter rules configured in the lemlist UI.
</Warning>

## Typical workflow

1. **Find contacts** — use `GET /contacts` with `search`, `email`, or `listId` to get contact IDs (`ctc_xxx`)
2. **Find or create a list** — use `GET /contacts/lists` to find an existing list, or `POST /contacts/lists` to create a new one
3. **Add contacts to the list** — call this endpoint with the contact IDs and list ID


## OpenAPI

````yaml post /contacts/lists/{listId}/entities
openapi: 3.0.0
info:
  title: lemlist API
  version: 1.0.0
  description: >-
    Welcome to the lemlist Developer Documentation.


    lemlist is very customizable and open. You'll find on this page all the API
    and integration you can do with lemlist.


    # Rate Limit


    lemlist's API rate limits requests in order to prevent abuse and overload of
    our services.  

    Rate limits are applied on all routes and per API key performing the
    request.  

    The rate limits are **20** requests per **2** seconds.  

    The response provides any information you may need about it:


    | Header | Description |

    | --- | --- |

    | Retry-After | The number of seconds in which you can retry |

    | X-RateLimit-Limit | The maximum requests in that time |

    | X-RateLimit-Remaining | The number of remaining requests you can make |

    | X-RateLimit-Reset | The date when the rate limit will reset |


    _Example of values for the rate limit headers_


    ``` json

    {
        "Retry-After": 2,
        "X-RateLimit-Limit": 20,
        "X-RateLimit-Remaining": 7,
        "X-RateLimit-Reset" : "Tue Feb 16 2021 09:02:42 GMT+0100 (Central European Standard Time)"
    }

     ```

    # Definitions


    ## Team


    A team is the entity of lemlist that can handle users and billing.


    ## Credits


    Credits are the coins a team uses to enrich emails, LinkedIn URLs, etc. via
    the enrich route. Each enrichment feature needs a certain amount of credits
    to run.


    ## User


    You use a user account to connect to lemlist and send messages via the
    connected emails or LinkedIn account.


    ## Campaign


    A campaign is the entity to automate outreach. A campaign has multiple
    sequences composed of steps.


    ## Lead


    A lead is a person that you try to contact via a campaign.


    ## Activity


    An activity is the history of all the steps.


    ## Unsubscribe


    An unsubscribe occurs when a person decides they don't want to receive
    emails from you anymore.


    # Authentication


    All API routes use the dedicated subdomain `api.lemlist.com`.


    lemlist uses API keys to allow access to the API. You can get your lemlist
    API key at our [integration
    page](https://app.lemlist.com/settings/integrations).


    You need to add the `Authorization` header using the `Basic` authentication
    type. `login:password` **where the login is always empty and the password is
    the API key**.


    ⚠️ **Don't forget to add the semicolon (**`:`**) before your API key in curl
    command.**


    > To authorize, use this code: 
      

    ``` shell

    curl https://api.lemlist.com/api/team \
      --user ":YourApiKey"

     ```

    **Make sure to replace** **`YourApiKey`** **with your API key.**


    # Give feedback


    If you want to report a bug, ask for data, or share with us a use case,
    please fill this [form](https://lemlist.typeform.com/to/mfVlkyGf). It will
    help us centralize your needs!
servers:
  - url: https://api.lemlist.com/api
security:
  - basicAuth: []
paths:
  /contacts/lists/{listId}/entities:
    parameters:
      - name: listId
        in: path
        required: true
        description: The unique identifier of the contact list (`clt_xxx` format)
        example: clt_abc123def456ghi78
        schema:
          type: string
          pattern: ^clt_[a-zA-Z0-9]+$
    post:
      tags:
        - Contacts
      summary: Add Contacts to List
      description: >-
        Adds existing CRM contacts to a static contact list. Contacts already in
        the list are silently skipped (no duplicates created). Cannot be used
        with dynamic lists.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              required:
                - contactIds
              properties:
                contactIds:
                  type: array
                  items:
                    type: string
                    pattern: ^ctc_[a-zA-Z0-9]+$
                  maxItems: 1000
                  description: >-
                    Array of contact IDs to add to the list (`ctc_xxx` format).
                    Maximum 1,000 per request.
            example:
              contactIds:
                - ctc_abc123def456ghi78
                - ctc_xyz789uvw012rst34
      responses:
        '200':
          description: Contacts added to list successfully
          content:
            application/json:
              schema:
                type: object
                properties:
                  message:
                    type: string
                  addedCount:
                    type: integer
                    description: Number of contacts added to the list
              example:
                message: Contacts added to list successfully
                addedCount: 2
        '400':
          description: >-
            Possible errors: Bad team / invalid listId / contactIds required /
            invalid contact ID format / list is not a contact list / cannot add
            to dynamic list
          content:
            text/plain:
              example: contactIds is required and must be a non-empty array
        '401':
          description: The authentication you supplied is incorrect
          content:
            text/plain:
              example: The authentication you supplied is incorrect
        '404':
          description: Contact list not found
          content:
            text/plain:
              example: Contact list not found
        '405':
          description: Method not allowed
components:
  securitySchemes:
    basicAuth:
      type: http
      scheme: basic

````