Agent Skills: Azure Cosmos DB SDK for Rust

Azure Cosmos DB SDK for Rust

Client library for Azure Cosmos DB NoSQL API — globally distributed, multi-model database.

Installation

cargo add azure_data_cosmos azure_identity

Environment Variables

COSMOS_ENDPOINT=https://<account>.documents.azure.com:443/
COSMOS_DATABASE=mydb
COSMOS_CONTAINER=mycontainer

Authentication

use azure_identity::DeveloperToolsCredential;
use azure_data_cosmos::CosmosClient;

let credential = DeveloperToolsCredential::new(None)?;
let client = CosmosClient::new(
    "https://<account>.documents.azure.com:443/",
    credential.clone(),
    None,
)?;

Client Hierarchy

| Client | Purpose | Get From | |--------|---------|----------| | CosmosClient | Account-level operations | Direct instantiation | | DatabaseClient | Database operations | client.database_client() | | ContainerClient | Container/item operations | database.container_client() |

Core Workflow

Get Database and Container Clients

let database = client.database_client("myDatabase");
let container = database.container_client("myContainer");

Create Item

use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize)]
struct Item {
    pub id: String,
    pub partition_key: String,
    pub value: String,
}

let item = Item {
    id: "1".into(),
    partition_key: "partition1".into(),
    value: "hello".into(),
};

container.create_item("partition1", item, None).await?;

Read Item

let response = container.read_item("partition1", "1", None).await?;
let item: Item = response.into_model()?;

Replace Item

let mut item: Item = container.read_item("partition1", "1", None).await?.into_model()?;
item.value = "updated".into();

container.replace_item("partition1", "1", item, None).await?;

Patch Item

use azure_data_cosmos::models::PatchDocument;

let patch = PatchDocument::default()
    .with_add("/newField", "newValue")?
    .with_remove("/oldField")?;

container.patch_item("partition1", "1", patch, None).await?;

Delete Item

container.delete_item("partition1", "1", None).await?;

Key Auth (Optional)

Enable key-based authentication with feature flag:

cargo add azure_data_cosmos --features key_auth

Best Practices

1. Always specify partition key — required for point reads and writes
2. Use into_model()? — to deserialize responses into your types
3. Derive Serialize and Deserialize — for all document types
4. Use Entra ID auth — prefer DeveloperToolsCredential over key auth
5. Reuse client instances — clients are thread-safe and reusable

Reference Links

| Resource | Link | |----------|------| | API Reference | https://docs.rs/azure_data_cosmos | | Source Code | https://github.com/Azure/azure-sdk-for-rust/tree/main/sdk/cosmos/azure_data_cosmos | | crates.io | https://crates.io/crates/azure_data_cosmos |

When to Use

This skill is applicable to execute the workflow or actions described in the overview.