Enum ResponseFormat 

#[non_exhaustive]
pub enum ResponseFormat {
    Free,
    JsonObject,
    JsonSchema {
        name: String,
        schema: Value,
    },
}

Constrain the model’s terminal (non-tool-call) reply shape. Default = Free.

Each model adapter translates this to the provider’s native format on the wire:

• OpenAI / DeepSeek: response_format: {type: "json_object"} for JsonObject; {type: "json_schema", json_schema: {name, schema, strict}} for JsonSchema. Providers that only support json_object (DeepSeek as of Dec 2025) degrade gracefully by injecting the schema into the system prompt instead.
• Gemini: generationConfig.responseMimeType = "application/json" plus generationConfig.responseSchema = <schema> for JsonSchema.
• Anthropic: no native field — adapters synthesise a “structured_output” tool with the schema, force tool_choice to it, and surface the tool’s args as the assistant text on response.

JsonSchema.schema is a serde_json::Value so callers can build it however they like — hand-rolled, via schemars::schema_for!(T), or pulled from a harness_loop::AgentLoop::run_typed<T>() derivation.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Free

Free-form text. The framework adds nothing to the request body.

JsonObject

“Reply with valid JSON of any shape.” Useful when the caller will run its own validation and doesn’t want to commit to a schema yet.

JsonSchema

“Reply with JSON matching this schema.” Adapters may need to sanitise dialect-specific keys before emitting (Gemini rejects $ref, OpenAI strict mode demands additionalProperties: false everywhere, …).

Fields

name: String

Short identifier — providers that require one (OpenAI) use it as the json_schema.name field.

schema: Value

JSON Schema, as a serde_json::Value.

Trait Implementations

impl Clone for ResponseFormat

fn clone(&self) -> ResponseFormat

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ResponseFormat

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for ResponseFormat

fn default() -> ResponseFormat

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for ResponseFormat

fn deserialize<__D>( __deserializer: __D, ) -> Result<ResponseFormat, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for ResponseFormat

fn serialize<__S>( &self, __serializer: __S, ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.