"Conversation API" is not a named product, so the closest matches are conversation and messaging APIs. Vonage Conversation exposes a Conversation API with create, retrieve and list operations 414, while Getstream provides chat and messaging APIs with SDKs for building in-app conversations 1. Twilio's Conversations product offers persistent multi-channel conversation APIs 3.

A question back: Which kind of conversation do you need: in-app chat, multi-channel messaging, or voice conversations with an AI agent?

1. 1

   Vonage Conversation APIvonage.comverified and signed

   Provides a Conversation API with createConversation, retrieveConversation and getuserConversations actions to create conversations and list user conversations 14.

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   official:API · Conversation APIAPI · Conversation API

   for agents: createConversation · retrieveConversation · getuserConversations

2. 2

   Stream Chat APIgetstream.ioverified and signed

   Offers chat and messaging APIs and SDKs for React, Swift, Android, Flutter and other platforms to build in-app conversations 111.

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   +1 community tools built for it

   for agents: conversation · chat · messaging

3. 3

   Twilio Conversationstwilio.comverified and signed

   Provides Conversations that persist across channels and sessions, connecting voice and messaging interactions into one continuous conversation 3.

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   official:SDK · twiliolibrary · Twilioskill · twilio-send-messageSDK · twilio+21 community tools built for it

   for agents: custom_api_call · api · api