Add a reaction to a message

POSThttps://api.postpress.ai/v1/messages/{message_id}/reaction

Attach an emoji reaction to a message on WhatsApp or LinkedIn. Sending a new reaction from the same account on the same message replaces the previous one.

Provider support: WhatsApp and LinkedIn only. Other providers return 403.

Authorization

X-API-KEYstringrequired
API key from your postpress dashboard. Sent as a request header.

Path parameters

message_idstringrequired
The id of the message to react to.

Request body

Send as application/json.

reactionstringrequired
Native emoji to react with, e.g. 👍. Provider rules apply (WhatsApp allows any emoji; LinkedIn accepts a fixed set).
{
  "reaction": "👍"
}

Response 200 OK

objectstringMessageReactionAddedrequired
successbooleanrequired
Always `true` when the reaction was registered with the provider.

Example request

curl --request POST \
  --url 'https://api.postpress.ai/api/v1/messages/msg_01HXYZ4QK3WJ8FN3M6QH7TZ8GR/reaction' \
  --header 'X-API-KEY: pp_live_...' \
  --header 'content-type: application/json' \
  --data '{
    "reaction": "👍"
  }'

Example response

{
  "object": "MessageReactionAdded",
  "success": true
}

Errors

Every error response follows the same envelope:

titlestringrequired
Short error title.
detailstringoptional
Human-readable explanation.
instancestringoptional
Request identifier for support.
typestringrequired
Error type identifier.
statusnumberrequired
HTTP status code.
401 Unauthorized13 types

Credentials are missing, expired, or otherwise invalid.

  • errors/missing_credentials - Some credentials are necessary to perform the request.
  • errors/multiple_sessions - LinkedIn limits multiple sessions on certain Recruiter accounts. Use the cookie connection method.
  • errors/invalid_checkpoint_solution - The checkpoint resolution did not pass successfully. Retry.
  • errors/invalid_proxy_credentials - The provided proxy credentials are invalid.
  • errors/checkpoint_error - The checkpoint does not appear to be resolvable.
  • errors/invalid_credentials - The provided credentials are invalid.
  • errors/expired_credentials - Credentials have expired. Reconnect the account.
  • errors/insufficient_privileges - This resource is out of your API-key scopes.
  • errors/disconnected_account - The account is disconnected from the provider service.
  • errors/disconnected_feature - The service you're trying to reach is disconnected.
  • errors/invalid_credentials_but_valid_account_imap - IMAP/SMTP credentials are invalid but the account is otherwise valid.
  • errors/expired_link - This link has expired. Generate a new one.
  • errors/wrong_account - The provided credentials do not match the correct account.
403 Forbidden9 types

Authenticated but the account is restricted or the action is not allowed.

  • errors/account_restricted - The account has been restricted by the provider.
  • errors/account_mismatch - This action cannot be done with your account.
  • errors/insufficient_permissions - Valid authentication but insufficient permissions to perform the request.
  • errors/session_mismatch - Token user id does not match client session id.
  • errors/feature_not_subscribed - The requested feature has not been subscribed or authenticated properly.
  • errors/subscription_required - A subscription is required to use this feature.
  • errors/unknown_authentication_context - An additional step seems necessary to complete login.
  • errors/action_required - An additional step is required.
  • errors/resource_access_restricted - You don't have access to this resource.
500 Internal Server Error3 types

Something went wrong on our side or with the upstream provider.

  • errors/unexpected_error - Something went wrong.
  • errors/provider_error - The provider is experiencing operational problems. Retry later.
  • errors/authentication_intent_error - The current authentication intent was killed after failure.
503 Service Unavailable5 types

postpress is temporarily unable to handle the request.

  • errors/no_client_session - No client session is currently running.
  • errors/no_channel - No channel to client session.
  • errors/no_handler - Handler missing for that request.
  • errors/network_down - Network is down on the server side. Retry shortly.
  • errors/service_unavailable - Service temporarily unavailable. Retry later.
504 Gateway Timeout1 types

The upstream provider did not respond in time.

  • errors/request_timeout - Request timed out. Retry, and contact support if it persists.
Updated May 2026