Struct MessageAttributes 

pub struct MessageAttributes {
    pub priority: u8,
    pub cacheable: bool,
    pub cache_type: Option<CacheType>,
    pub cache_key: Option<String>,
    pub category: MessageCategory,
    pub metadata: HashMap<String, Value>,
}

Attributes that guide how providers handle a message.

These attributes control caching behavior, message ordering, and provide metadata that providers can use for optimization.

Caching

For Anthropic’s prompt caching, set cacheable: true and optionally specify a CacheType. The cache_key helps identify content for deduplication across requests.

Priority

Priority determines message ordering when using UnifiedLLMRequest::sort_messages(). Lower values = higher priority (processed first). Range: 0-255.

Example

use multi_llm::{MessageAttributes, MessageCategory, CacheType};
use std::collections::HashMap;

// Cacheable system instruction with highest priority
let system_attrs = MessageAttributes {
    priority: 0,
    cacheable: true,
    cache_type: Some(CacheType::Extended),
    cache_key: Some("system-v1".to_string()),
    category: MessageCategory::SystemInstruction,
    metadata: HashMap::new(),
};

// Current user message (not cached, lowest priority)
let user_attrs = MessageAttributes::default();  // priority=50, cacheable=false

Fields

priority: u8

Priority for message ordering (lower = higher priority).

Default is 50. Range: 0 (highest) to 255 (lowest). Used by UnifiedLLMRequest::sort_messages() to order messages.

cacheable: bool

Whether this message content is static and can be cached.

When true, providers that support caching (like Anthropic) will attempt to cache this content for subsequent requests.

cache_type: Option<CacheType>

Cache TTL type for Anthropic prompt caching.

• CacheType::Ephemeral: 5-minute TTL, 1.25x write cost
• CacheType::Extended: 1-hour TTL, 2x write cost

Only meaningful when cacheable is true. Ignored by providers that don’t support prompt caching.

cache_key: Option<String>

Optional cache key for content deduplication.

When provided, helps identify identical content across requests. Useful for versioning system prompts (e.g., “system-v2”).

category: MessageCategory

Semantic category for provider-specific handling.

See MessageCategory for details on how categories affect caching and priority defaults.

metadata: HashMap<String, Value>

Custom metadata for application-specific extensions.

This data is passed through but not interpreted by multi-llm. Useful for tracking, logging, or application-specific processing.

Trait Implementations

impl Clone for MessageAttributes

fn clone(&self) -> MessageAttributes

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MessageAttributes

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

Formats the value using the given formatter.

impl Default for MessageAttributes

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for MessageAttributes

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for MessageAttributes

fn eq(&self, other: &MessageAttributes) -> 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 MessageAttributes

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 MessageAttributes