Permission cards in Rust

Use golem_rust::schema::wit::GuestPermissionCardHandle in an agent or tool input/output. It has the required IntoSchema and FromSchema implementations:

use golem_rust::schema::wit::GuestPermissionCardHandle;
 
async fn forward(card: GuestPermissionCardHandle) -> GuestPermissionCardHandle {
    ReceiverClient::get("target".to_string())
        .accept(card)
        .await
}

Cards are opaque affine capabilities. Encoding a call transfers the card, so do not serialize, clone for reuse, persist, or send the same handle twice. This guide covers transferring an already received handle. The SDK does not currently expose a supported high-level constructor for wrapping cards returned by the lower-level permissions host bindings. Do not use hidden schema-codec constructors as application APIs, invent authority locally, or log card internals.