Enum FunctionCallingMode 

#[non_exhaustive]
pub enum FunctionCallingMode {
    Auto,
    Any,
    None,
    Validated,
    Unknown {
        mode_type: String,
        data: Value,
    },
}

Modes for function calling behavior.

This enum is marked #[non_exhaustive] for forward compatibility. New modes may be added in future versions.

Forward Compatibility (Evergreen Philosophy)

When the API returns a mode value that this library doesn’t recognize, it will be captured as FunctionCallingMode::Unknown rather than causing a deserialization error. This follows the Evergreen spec philosophy of graceful degradation.

Modes

• Auto (default): Model decides whether to call functions or respond naturally
• Any: Model must call a function; guarantees schema adherence for calls
• None: Prohibits function calling entirely
• Validated (Preview): Ensures either function calls OR natural language adhere to schema

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.

Auto

Model decides whether to call functions or respond with natural language.

Any

Model must call a function; guarantees schema adherence for calls.

None

Function calling is disabled.

Validated

Ensures either function calls OR natural language adhere to schema.

This is a preview mode that provides schema adherence guarantees for both function call outputs and natural language responses.

Unknown

Unknown mode (for forward compatibility).

This variant captures any unrecognized mode values from the API, allowing the library to handle new modes gracefully.

The mode_type field contains the unrecognized mode string, and data contains the JSON value (typically the same string).

Fields

mode_type: String

The unrecognized mode string from the API

data: Value

The raw JSON value, preserved for debugging

Implementations

impl FunctionCallingMode

pub const fn is_unknown(&self) -> bool

Check if this is an unknown mode.

pub fn unknown_mode_type(&self) -> Option<&str>

Returns the mode type name if this is an unknown mode.

Returns None for known modes.

pub fn unknown_data(&self) -> Option<&Value>

Returns the raw JSON data if this is an unknown mode.

Returns None for known modes.

Trait Implementations

impl Clone for FunctionCallingMode

fn clone(&self) -> FunctionCallingMode

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for FunctionCallingMode

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for FunctionCallingMode

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for FunctionCallingMode

fn eq(&self, other: &FunctionCallingMode) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for FunctionCallingMode

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for FunctionCallingMode