Message Part Types

Messages use a parts array to represent content. The part types differ between request (what you send) and response (what the API returns). Both follow the AI SDK UIMessage format.

Request Parts

These are the part types you can include in the parts array when sending a message via POST /api/chat:

Part Type	Fields	Description
`text`	`text`	User’s text message
`file`	`mediaType`, `url`, `filename?`	File attachment — `url` must be a data URL

At minimum, include one text part. Example:


{
  "parts": [
    { "type": "text", "text": "What's in this image?" },
    { "type": "file", "mediaType": "image/png", "url": "data:image/png;base64,..." }
  ]
}

Response Parts

These are the part types the Pandora API can emit in assistant messages, both during streaming and in stored thread history:

Part Type	Fields	When Emitted
`text`	`text`, `state?` (`'streaming'` \| `'done'`)	Always — LLM text output
`tool-{name}`	`toolCallId`, `state`, `input`, `output`, `errorText`	When the agent calls a tool
`reasoning`	`text`, `state?`, `providerMetadata?`	When the model supports reasoning/thinking
`source-url`	`sourceId`, `url`, `title?`, `providerMetadata?`	When the model provides citations
`file`	`mediaType`, `url`, `filename?`	When the response includes files
`step-start`	—	At the start of each agent step

Tool parts have dynamic type names like tool-current-time or tool-web-search. Check for the tool- prefix when rendering.

Tool Part States

Tool parts go through a lifecycle indicated by the state field:

State	Meaning
`partial-call`	Tool is being called — `input` is still streaming in
`call`	Tool call is complete — `input` is final, waiting for result
`approval-requested`	Tool requires user approval before executing. The part includes an `approval` object with `{ id: string }` containing the run ID. Use `POST /api/chat/approve` to approve or deny.
`input-available`	Tool input is ready (intermediate state before execution)
`output-available`	Tool finished — `output` contains the result
`error`	Tool failed — `errorText` contains the error message