[key: string]:
  | undefined
  | string
  | number
  | boolean
  | {
  content:   | string
     | (
     | {
     text: string;
     type: "text";
   }
     | {
     file_id: string;
     type: "file";
   })[];
  role:   | "function"
     | "agent"
     | "tool"
     | "assistant"
     | "developer"
     | "system"
     | "user";
  tool_call_id?: null | string;
  tool_calls?: null | object[];
}
  | string[]
  | Date
  | Document
  | Record<string, string>
  | Document[]
  | JsonArray
  | Record<string, string>[]
  | object[]
  | Record<string, string>[]
  | SingleMetricValue[]
| Record<string, SingleMetricValue>

createdAt: Date;

optional datasetInput: string;

optional datasetMetadata: Record<string, string>;

optional datasetOutput: string;

optional externalId: string;

optional id: string;

optional input: StepAllowedInputType;

optional metadata: Record<string, string>;

optional metrics: object;

optional durationNs: number;

optional numCachedInputTokens: number;

optional numInputTokens: number;

optional numOutputTokens: number;

optional numReasoningTokens: number;

optional numTotalTokens: number;

optional timeToFirstTokenNs: number;

optional name: string;

optional output:
  | JsonArray
  | StepAllowedOutputType;

optional redactedInput: StepAllowedInputType;

optional redactedOutput:
  | JsonArray
  | StepAllowedOutputType;

optional statusCode: number;

optional stepNumber: number;

optional tags: string[];

type:
  | "agent"
  | "llm"
  | "retriever"
  | "tool"
  | "workflow"
  | "control"
  | "trace"
  | "session";

userMetadata: Record<string, string>;