AI SDK Kotlin/ai.torad.aisdk/StreamEvent/ToolError

ToolError

@Serializable

data class ToolError(val toolCallId: String, val toolName: String, val message: String, val error: AgentError? = null, val providerMetadata: Map<String, JsonElement>? = null) : StreamEvent

Tool execution failed. error carries the typed AgentError (NoSuchTool / InvalidToolInput / ToolExecution / ToolCallRepairFailed) so in-process consumers can when (event.error) instead of substring-matching message. @Transient — it's dropped on serialization (AgentError isn't @Serializable); message is the wire-stable rendering and stays the single source of display text.