# ModelSubject The subject type for language model evaluations. ``` struct ModelSubject where Value : Decodable, Value : Encodable, Value : Sendable ``` ## Overview Carries the value the model produces and an optional structured transcript. The transcript is required for tool-call evaluation. [`ToolCallEvaluator`](/documentation/Evaluations/ToolCallEvaluator) performs a runtime check and throws [`EvaluationError.missingTranscript(evaluatorType:)`](/documentation/Evaluations/EvaluationError/missingTranscript(evaluatorType:)) if the transcript is `nil`. ```swift let subject = ModelSubject(value: "Paris, France") ``` ## Topics ### Creating a subject [`init(value: Value, transcript: StructuredTranscript?)`](/documentation/Evaluations/ModelSubject/init(value:transcript:)) Creates a model subject with a value and optional transcript. ### Accessing the content [`var value: Value`](/documentation/Evaluations/ModelSubject/value) The typed value the model produces. [`var transcript: StructuredTranscript?`](/documentation/Evaluations/ModelSubject/transcript) The structured transcript from the model session. ### Inspecting tool calls [`var toolCalls: [Transcript.ToolCall]`](/documentation/Evaluations/ModelSubject/toolCalls) The tool calls from the transcript, or an empty array if no transcript was provided. [`struct StructuredTranscript`](/documentation/Evaluations/StructuredTranscript) ## Relationships ### Conforms To [`SendableMetatype`](/documentation/Swift/SendableMetatype) [`EvaluationSubject`](/documentation/Evaluations/EvaluationSubject) [`Sendable`](/documentation/Swift/Sendable) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)