Send a chat message

post

https://api.getkronos.ai/api/chat

Sends a message to an agent and returns its reply. This is the core endpoint of the API distribution channel.

Response mode

Streaming (default when messages is provided, or stream: true) — a text/event-stream of Server-Sent Events (Vercel AI UI message stream; x-vercel-ai-ui-message-stream: v1).
JSON (stream: false) — a single JSON object with the agent reply.

The reply always comes from the agent configured on the API distribution that owns the key; the request-level agent_id is ignored on API-key calls. Pass conversation_id to continue an existing thread.

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Body Params

messages

array of objects

Conversation history in useChat format. The last user message is the prompt. Provide either messages or message.

messages

message

string

Legacy single-message field. Use messages for new integrations.

agent_id

uuid

The agent to send the message to. On API-key-authenticated requests this is ignored — the reply always comes from the agent configured on the API distribution that owns the key.

agent_version_id

uuid

Pin the response to a specific published agent version.

conversation_id

uuid

Continue an existing conversation. Omit to start a new one.

channel

string

Channel label recorded on the conversation (for analytics and routing).

source

string

Free-form source label recorded on the conversation.

show_citations

boolean

Defaults to false

Include source citations in the response.

show_reasoning

boolean

Defaults to false

Include the agent reasoning trace in the response.

show_tool_calls

boolean

Defaults to false

Include tool-call events in the response.

contact_email

string

Visitor's email. Attaches the conversation to a contact.

contact_name

string

Visitor's name. Attaches the conversation to a contact.

visitor_token

string

Stable visitor token that ties messages to one contact across requests. Reuse the value returned on the first response.

attachments

array of objects

File attachment references (e.g. the result of POST /chat/upload).

attachments

stream

boolean

Stream the response as Server-Sent Events. Defaults to true when messages is provided, false otherwise. When false, a single JSON object is returned.

Responses

200

Agent reply. An SSE stream when streaming, or a single JSON object when stream is false.

400

Message content is required.