contextvm-sdk

Rust SDK for the ContextVM protocol — MCP over Nostr.

A complete implementation enabling Model Context Protocol (MCP) servers and clients to communicate over the Nostr network with decentralized discovery, cryptographic identity, and optional end-to-end encryption.

Architecture

┌──────────────────────────────────────────────────────────┐
│                    Your Application                       │
├──────────────┬───────────────┬────────────────────────────┤
│   Gateway    │     Proxy     │        Discovery           │
│  (server →   │  (nostr →     │  (find servers &           │
│    nostr)    │    client)    │   capabilities)            │
├──────────────┴───────────────┴────────────────────────────┤
│                    Transport Layer                         │
│            NostrServerTransport / NostrClientTransport     │
├───────────────────────────────────────────────────────────┤
│  Core          │  Encryption     │  Relay    │  Signer    │
│  (types,       │  (NIP-44,       │  (pool    │  (key      │
│   JSON-RPC,    │   NIP-59        │   mgmt)   │   mgmt)    │
│   validation)  │   gift wrap)    │           │            │
├────────────────┴─────────────────┴───────────┴────────────┤
│                   Nostr Network (relays)                   │
└───────────────────────────────────────────────────────────┘

Protocol

ContextVM maps MCP's JSON-RPC 2.0 messages onto Nostr events:

Kind	Name	Type	Description
25910	ContextVM Messages	Ephemeral	MCP request/response/notification
1059	Gift Wrap (NIP-59)	Regular	Encrypted MCP messages
11316	Server Announcement	Addressable	Server identity & metadata
11317	Tools List	Addressable	Published tool capabilities
11318	Resources List	Addressable	Published resource capabilities
11319	Resource Templates	Addressable	Published resource template list
11320	Prompts List	Addressable	Published prompt capabilities

Messages are routed using Nostr p tags (recipient pubkey) and correlated with e tags (request event ID).

Installation

Add to your Cargo.toml:

[dependencies]
contextvm-sdk = { git = "https://github.com/k0sti/rust-contextvm-sdk" }

Or clone and use as a path dependency:

[dependencies]
contextvm-sdk = { path = "../rust-contextvm-sdk" }

Quick Start

Gateway — Expose a Local MCP Server via Nostr

use contextvm_sdk::gateway::{NostrMCPGateway, GatewayConfig};
use contextvm_sdk::transport::server::NostrServerTransportConfig;
use contextvm_sdk::core::types::{ServerInfo, EncryptionMode};
use contextvm_sdk::signer;

#[tokio::main]
async fn main() -> contextvm_sdk::Result<()> {
    let keys = signer::generate();

    let config = GatewayConfig {
        nostr_config: NostrServerTransportConfig {
            relay_urls: vec!["wss://relay.damus.io".into()],
            encryption_mode: EncryptionMode::Optional,
            server_info: Some(ServerInfo {
                name: Some("My MCP Server".into()),
                about: Some("Tools via Nostr".into()),
                ..Default::default()
            }),
            is_announced_server: true,
            ..Default::default()
        },
    };

    let mut gateway = NostrMCPGateway::new(keys, config).await?;
    let mut requests = gateway.start().await?;
    gateway.announce().await?;

    while let Some(req) = requests.recv().await {
        println!("Request: {:?}", req.message);
        // Process and respond:
        // gateway.send_response(&req.event_id, response).await?;
    }
    Ok(())
}

Proxy — Connect to a Remote MCP Server via Nostr

use contextvm_sdk::proxy::{NostrMCPProxy, ProxyConfig};
use contextvm_sdk::transport::client::NostrClientTransportConfig;
use contextvm_sdk::core::types::EncryptionMode;
use contextvm_sdk::signer;

#[tokio::main]
async fn main() -> contextvm_sdk::Result<()> {
    let keys = signer::generate();

    let config = ProxyConfig {
        nostr_config: NostrClientTransportConfig {
            relay_urls: vec!["wss://relay.damus.io".into()],
            server_pubkey: "abc123...server_hex_pubkey".into(),
            encryption_mode: EncryptionMode::Optional,
            ..Default::default()
        },
    };

    let mut proxy = NostrMCPProxy::new(keys, config).await?;
    let mut responses = proxy.start().await?;

    // Send an MCP request
    let request = contextvm_sdk::JsonRpcMessage::Request(contextvm_sdk::JsonRpcRequest {
        jsonrpc: "2.0".into(),
        id: serde_json::json!(1),
        method: "tools/list".into(),
        params: None,
    });
    proxy.send(&request).await?;

    // Receive response
    if let Some(msg) = responses.recv().await {
        println!("Response: {:?}", msg);
    }
    Ok(())
}

Discovery — Find MCP Servers on Nostr

use contextvm_sdk::{discovery, signer, RelayPool};

#[tokio::main]
async fn main() -> contextvm_sdk::Result<()> {
    let keys = signer::generate();
    let pool = RelayPool::new(keys).await?;
    let relays = vec!["wss://relay.damus.io".into()];
    pool.connect(&relays).await?;

    let servers = discovery::discover_servers(pool.client(), &relays).await?;
    for server in &servers {
        println!("Server: {} ({:?})", server.pubkey, server.server_info.name);

        let tools = discovery::discover_tools(pool.client(), &server.pubkey_parsed, &relays).await?;
        println!("  Tools: {}", tools.len());
    }
    Ok(())
}

Module Overview

Module	Description
core	Protocol constants, JSON-RPC types, error types, validation
transport	Client/server Nostr transports with event loop and correlation
gateway	High-level gateway bridging local MCP servers to Nostr
proxy	High-level proxy connecting to remote MCP servers via Nostr
discovery	Server/capability discovery via addressable Nostr events
encryption	NIP-44 encryption and NIP-59 gift wrapping
relay	Nostr relay pool management (connect, publish, subscribe)
signer	Key generation and management utilities

Configuration

Encryption Modes

Mode	Behavior
Optional	Encrypt responses if the incoming request was encrypted
Required	All messages must be encrypted (rejects plaintext)
Disabled	No encryption; all messages sent as plaintext kind 25910

Encryption uses NIP-44 for payload encryption and NIP-59 (Gift Wrap) for metadata-private delivery. Server announcements (kinds 11316–11320) are always public.

Server Transport Config

Field	Default	Description
relay_urls	["wss://relay.damus.io"]	Nostr relays to connect to
encryption_mode	Optional	Encryption policy
server_info	None	Server metadata for announcements
is_announced_server	false	Whether to publish announcements (CEP-6)
allowed_public_keys	[] (allow all)	Client pubkey allowlist (hex)
excluded_capabilities	[]	Methods exempt from allowlist
session_timeout	300s	Inactive session expiry

Client Transport Config

Field	Default	Description
relay_urls	["wss://relay.damus.io"]	Nostr relays to connect to
server_pubkey	(required)	Target server's public key (hex)
encryption_mode	Optional	Encryption policy
is_stateless	false	Emulate initialize locally
timeout	30s	Response timeout

References

• ContextVM Specification
• ContextVM TypeScript SDK
• Model Context Protocol
• Nostr Protocol
• NIP-44 Encryption
• NIP-59 Gift Wrap

License

MIT