Token Store

The token store interface allows pluggable token persistence. Implement the TokenStore trait for custom backends (SQLite, Redis, filesystem, keyring, ...):

use async_trait::async_trait;
use rust_mcp_sdk::auth::{TokenResponse, TokenStore, TokenStoreError};

struct MyTokenStore;

#[async_trait]
impl TokenStore for MyTokenStore {
    async fn get_access_token(&self) -> Option<String> {
        // Retrieve the access token from disk, keyring, or database
        todo!()
    }

    async fn get_refresh_token(&self) -> Option<String> {
        // Retrieve the refresh token, if any
        todo!()
    }

    async fn set_tokens(&self, token: TokenResponse) -> Result<(), TokenStoreError> {
        // Persist access + refresh tokens
        todo!()
    }

    async fn clear(&self) -> Result<(), TokenStoreError> {
        // Remove tokens (e.g., on logout or failed refresh)
        todo!()
    }

    // Optional: hint that a stored token should be refreshed.
    // Defaults to false.
    async fn needs_refresh(&self) -> bool {
        false
    }
}

All methods are async to accommodate I/O-bound backends.

Wiring it in

use std::sync::Arc;
use rust_mcp_sdk::auth::McpAuthConfig;

let client = McpAuthConfig::builder()
    .server_url("https://mcp.example.com/mcp")
    .token_store(Arc::new(MyTokenStore))
    .build()?;

The client uses the store on every get_auth_headers()/get_token() call: it returns the cached access token when available, tries the refresh token next, and falls back to full re-authentication after a clear().

Built-in implementations

• InMemoryTokenStore - thread-safe in-memory storage; used by default when no store is configured

There is no built-in file-backed store - implement TokenStore for your persistence layer of choice.