Trait Invocable 

pub trait Invocable: Send + Sync {
    // Required methods
    fn spec(&self) -> &InvocableSpec;
    fn invoke<'life0, 'life1, 'life2, 'async_trait>(
        &'life0 self,
        request: InvocableRequest,
        ctx: &'life1 mut CapabilityContext<'life2>,
    ) -> Pin<Box<dyn Future<Output = Result<InvocableResult, CapabilityError>> + Send + 'async_trait>>
       where Self: 'async_trait,
             'life0: 'async_trait,
             'life1: 'async_trait,
             'life2: 'async_trait;
}

A capability that the model can invoke during a conversation turn.

Implement this trait to expose custom functionality – database queries, API calls, file operations, code execution – to the agentic loop. Each implementor provides a spec describing the capability and an async invoke method that performs the work.

The agentkit loop discovers invocables through a CapabilityProvider and presents them to the model alongside regular tools.

Example

use agentkit_capabilities::{
    CapabilityContext, CapabilityError, CapabilityName, Invocable,
    InvocableOutput, InvocableRequest, InvocableResult, InvocableSpec,
};
use async_trait::async_trait;
use serde_json::json;

struct CurrentTime {
    spec: InvocableSpec,
}

impl CurrentTime {
    fn new() -> Self {
        Self {
            spec: InvocableSpec::new(
                CapabilityName::new("current_time"),
                "Return the current UTC time",
                json!({ "type": "object" }),
            ),
        }
    }
}

#[async_trait]
impl Invocable for CurrentTime {
    fn spec(&self) -> &InvocableSpec {
        &self.spec
    }

    async fn invoke(
        &self,
        _request: InvocableRequest,
        _ctx: &mut CapabilityContext<'_>,
    ) -> Result<InvocableResult, CapabilityError> {
        Ok(InvocableResult::text("2026-03-22T12:00:00Z"))
    }
}

Required Methods

fn spec(&self) -> &InvocableSpec

Returns the specification that describes this capability to the model.

fn invoke<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, request: InvocableRequest, ctx: &'life1 mut CapabilityContext<'life2>, ) -> Pin<Box<dyn Future<Output = Result<InvocableResult, CapabilityError>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait,

Executes the capability with the given request and context.

Arguments

• request - The invocation request containing the model-provided input and session identifiers.
• ctx - The shared capability context for this turn.

Errors

Returns CapabilityError if the capability is unavailable, the input is invalid, or execution fails.

Implementors