Server-lessComposable Derive Macros for Rust

Quick Example ​

use server_less::prelude::*;

struct UserService { /* ... */ }

#[http(prefix = "/api")]
#[cli(name = "users")]
#[mcp(namespace = "users")]
#[ws(path = "/ws")]
impl UserService {
    /// Create a new user
    pub async fn create_user(&self, name: String, email: String) -> Result<User, UserError> {
        // your implementation
    }

    /// Get user by ID
    pub async fn get_user(&self, id: String) -> Option<User> {
        // your implementation
    }
}

This generates:

• HTTP: Axum router with POST /api/users, GET /api/users/{id} + OpenAPI spec
• CLI: Clap commands: users create-user --name X --email Y
• MCP: Model Context Protocol tools: users_create_user, users_get_user
• WebSocket: JSON-RPC 2.0 over WebSocket

Available Macros ​

Runtime Protocols (6) ​

Generate working server implementations:

• #[http] - REST/HTTP with Axum + OpenAPI ✅ Production Ready
• #[cli] - Command-line with Clap ✅ Production Ready
• #[mcp] - Model Context Protocol ✅ Production Ready
• #[ws] - WebSocket JSON-RPC 2.0 ✅ Stable
• #[jsonrpc] - Standalone JSON-RPC ✅ Stable
• #[graphql] - GraphQL schema + resolvers ✅ Working*

Schema Generators (5) ​

Generate IDL/schema files:

• #[grpc] - Protocol Buffers .proto files
• #[capnp] - Cap'n Proto .capnp schemas
• #[thrift] - Apache Thrift .thrift IDL
• #[smithy] - AWS Smithy .smithy models
• #[connect] - Connect RPC schemas

Specification Generators (4) ​

Generate API documentation:

• #[openrpc] - OpenRPC specs (JSON-RPC docs)
• #[asyncapi] - AsyncAPI specs (WebSocket/messaging)
• #[jsonschema] - JSON Schema definitions
• #[markdown] - Human-readable API docs

Blessed Presets (4) ​

Batteries-included shortcuts:

• #[server] → #[http] + #[serve(http)]
• #[rpc] → #[jsonrpc] + #[openrpc] + #[serve(jsonrpc)]
• #[tool] → #[mcp] + #[jsonschema]
• #[program] → #[cli] + #[markdown]

Utilities ​

• #[derive(ServerlessError)] - Error code inference + HTTP status mapping
• #[serve] - Compose multiple protocol routers
• #[route] - Per-method HTTP overrides
• #[param] - Per-parameter cross-protocol customization

Project Status ​

Current: v0.2.0 ✅

• 18 macros implemented across 6 crates
• 466 tests passing, 0 failures
• Blessed presets: #[server], #[rpc], #[tool], #[program]
• Mount points for nested subcommand composition
• CLI output formatting with --json, --jq, --output-schema
• Published on crates.io

See TODO.md for the backlog.

Design Philosophy ​

Server-less follows four core principles:

1. Minimize Barrier to Entry - The simple case should be trivial: #[derive(Server)]
2. Progressive Disclosure - Complexity appears only when you need it
3. Gradual Refinement - Start simple, incrementally add control
4. Not Here to Judge - Support multiple workflows, don't prescribe

Read more: Impl-First Design

Part of RHI ​

Server-less is part of the RHI ecosystem - tools for building composable systems.

Related projects:

• Lotus - Object store (uses Server-less for server setup)
• Spore - Lua runtime with LLM integration
• Hypha - Async runtime primitives

Getting Started ​

1. REST API Tutorial - Build a blog API in 30 minutes
2. Multi-Protocol Tutorial - Expose one service over HTTP, CLI, MCP, and more
3. Design Philosophy - Understand the impl-first approach
4. Param Attributes - #[param] cross-protocol customization

Installation ​

[dependencies]
# Get everything (recommended for getting started)
server-less = "0.2"

# Or select specific features
server-less = { version = "0.2", default-features = false, features = ["http", "cli", "mcp"] }

Contributing ​

Contributions welcome! See CLAUDE.md for development guidelines.

License ​

MIT License - see LICENSE for details.