Resources

In the Basics chapter, we learned how to read a resource. In this section, we’ll explore in more detail how deal with resources provided by the MCP server.

Reading a Resource

To read a resource, use the read_resource() method. It requires the tool name and optional arguments.

use neva::prelude::*;

#[tokio::main]
async fn main() -> Result<(), Error> {
    let mut client = Client::new()
        .with_options(|opt| opt
            .with_stdio(
                "cargo", 
                ["run", "--manifest-path", "./neva-mcp-server/Cargo.toml"]));

    client.connect().await?;

    let resource = client.read_resource("res://resource-1").await?

    println!("{:?}", result.contents);

    client.disconnect().await
}

Contents

In the example above, the read_resource method returns a ReadResourceResult, which contains a Vec of ResourceContents.

You can access individual resource fields using the following methods:

• uri()
• title()
• mime()
• annotations()
• text() — returns the text content
• blob() — returns the binary (blob) content
• json() — returns the JSON content

Subscribing to resource updates

When the list of available resources changes on the server, and the MCP server has declared listChanged, it will publish a notifications/resources/list_changed notification. On the client side, you can subscribe to it as follows:

client.on_resources_changed(|_: Notification| async {
    println!("Resource list has been updated");
});

Additionally, when a specific resource is updated on the server, a notifications/resources/updated notification is sent. You can subscribe or unsubscribe from these updates using:

client.on_resource_changed(|n: Notification| async move {
    let params = n.params::<SubscribeRequestParams>()
        .expect("Expected SubscribeRequestParams");

    println!("Resource '{}' has been updated", params.uri); 
});

client.subscribe_to_resource("res://some-resource").await?;

// ...

client.unsubscribe_from_resource("res://some-resource").await?;

Learn By Example

Here you may find the full example

Additional examples

• Subscription to the resource updates