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POST
Create a new message in a chat via API key

Authorizations

Authorization
string
header
required

Enter your LeanMCP API key

Body

application/json
chatId
string
required

Chat ID this message belongs to (UUID)

Example:

"c1a83d84-7154-464c-bd19-a9f10e0a067f"

role
enum<string>
required

Role of the message sender

Available options:
system,
assistant,
user
content
string
required

Message content/text

id
string

Pre-generated message ID (UUID). Auto-generated if not provided

Example:

"abc123-def456-789-ghi-012345678901"

messageIndex
number

Order of message in chat (0-based). Auto-calculated if not provided

Required range: x >= 0
Example:

0

metadata
object

Additional metadata for the message

fileIds
string[]

Array of file IDs to associate with this message

Example:

Response

Message created successfully

id
string
required

Unique message identifier (UUID)

chatId
string
required

Chat ID this message belongs to (UUID)

Example:

"c1a83d84-7154-464c-bd19-a9f10e0a067f"

userId
string
required

User ID who owns this message

role
enum<string>
required

Role of the message sender

Available options:
system,
assistant,
user
content
string
required

Message content/text

messageIndex
number
required

Order of message in the chat (0-based)

Required range: x >= 0
createdAt
string
required

Timestamp when message was created

updatedAt
string
required

Timestamp when message was last updated

metadata
object

Additional metadata for the message