Development Guidelines

This document provides comprehensive guidelines for developers contributing to ADK-Rust. Following these standards ensures code quality, consistency, and maintainability across the project.

Table of Contents

• Getting Started
• Project Structure
• Code Style
• Error Handling
• Async Patterns
• Testing
• Documentation
• Pull Request Process
• Common Tasks

Getting Started

Prerequisites

• Rust: 1.75 or higher (check with rustc --version)
• Cargo: Latest stable
• Git: For version control

Setting Up Your Environment

# Clone the repository
git clone https://github.com/zavora-ai/adk-rust.git
cd adk-rust

# Build the project
cargo build

# Run all tests
cargo test --all

# Check for lints
cargo clippy --all-targets --all-features

# Format code
cargo fmt --all

Environment Variables

For running examples and tests that require API keys:

# Gemini (default provider)
export GOOGLE_API_KEY="your-api-key"

# OpenAI (optional)
export OPENAI_API_KEY="your-api-key"

# Anthropic (optional)
export ANTHROPIC_API_KEY="your-api-key"

Project Structure

ADK-Rust is organized as a Cargo workspace with multiple crates:

adk-rust/
├── adk-core/       # Foundational traits and types (Agent, Tool, Llm, Event)
├── adk-telemetry/  # OpenTelemetry integration
├── adk-model/      # LLM providers (Gemini, OpenAI, Anthropic)
├── adk-tool/       # Tool system (FunctionTool, MCP, AgentTool)
├── adk-session/    # Session management (in-memory, SQLite)
├── adk-artifact/   # Binary artifact storage
├── adk-memory/     # Long-term memory with search
├── adk-agent/      # Agent implementations (LlmAgent, workflow agents)
├── adk-runner/     # Execution runtime
├── adk-server/     # REST API and A2A protocol
├── adk-cli/        # Command-line launcher
├── adk-realtime/   # Voice/audio streaming agents
├── adk-graph/      # LangGraph-style workflows
├── adk-browser/    # Browser automation tools
├── adk-eval/       # Agent evaluation framework
├── adk-rust/       # Umbrella crate (re-exports all)
└── examples/       # Working examples

Crate Dependencies

Crates must be published in dependency order:

1. adk-core (no internal deps)
2. adk-telemetry
3. adk-model
4. adk-tool
5. adk-session
6. adk-artifact
7. adk-memory
8. adk-agent
9. adk-runner
10. adk-server
11. adk-cli
12. adk-realtime
13. adk-graph
14. adk-browser
15. adk-eval
16. adk-rust (umbrella)

Code Style

General Principles

1. Clarity over cleverness: Write code that is easy to read and understand
2. Explicit over implicit: Prefer explicit types and error handling
3. Small functions: Keep functions focused and under 50 lines when possible
4. Meaningful names: Use descriptive variable and function names

Formatting

Use rustfmt with default settings:

cargo fmt --all

The CI pipeline enforces formatting. Always run cargo fmt before committing.

Naming Conventions

Imports

Organize imports in this order:

// 1. Standard library
use std::collections::HashMap;
use std::sync::Arc;

// 2. External crates
use async_trait::async_trait;
use serde::{Deserialize, Serialize};
use tokio::sync::RwLock;

// 3. Internal crates (adk-*)
use adk_core::{Agent, Event, Result};

// 4. Local modules
use crate::config::Config;
use super::utils;

Clippy

All code must pass clippy with no warnings:

cargo clippy --all-targets --all-features

Address clippy warnings rather than suppressing them. If suppression is necessary, document why:

#[allow(clippy::too_many_arguments)]
// Builder pattern requires many parameters; refactoring would hurt usability
fn complex_builder(...) { }

Error Handling

Use adk_core::AdkError

All errors should use the centralized error type:

use adk_core::{AdkError, Result};

// Return Result<T> (aliased to Result<T, AdkError>)
pub async fn my_function() -> Result<String> {
    // Use ? for propagation
    let data = fetch_data().await?;

    // Create errors with appropriate variants
    if data.is_empty() {
        return Err(AdkError::Tool("No data found".into()));
    }

    Ok(data)
}

Error Variants

Use the appropriate error variant:

Error Messages

Write clear, actionable error messages:

// Good: Specific and actionable
Err(AdkError::Config("API key not found. Set GOOGLE_API_KEY environment variable.".into()))

// Bad: Vague
Err(AdkError::Config("Invalid config".into()))

Async Patterns

Use Tokio

All async code uses the Tokio runtime:

use tokio::sync::{Mutex, RwLock};

// Prefer RwLock for read-heavy data
let state: Arc<RwLock<State>> = Arc::new(RwLock::new(State::default()));

// Use Mutex for write-heavy or simple cases
let counter: Arc<Mutex<u32>> = Arc::new(Mutex::new(0));

Async Traits

Use async_trait for async trait methods:

use async_trait::async_trait;

#[async_trait]
pub trait MyTrait: Send + Sync {
    async fn do_work(&self) -> Result<()>;
}

Streaming

Use EventStream for streaming responses:

use adk_core::EventStream;
use async_stream::stream;
use futures::Stream;

fn create_stream() -> EventStream {
    let s = stream! {
        yield Ok(Event::new("inv-1"));
        yield Ok(Event::new("inv-2"));
    };
    Box::pin(s)
}

Thread Safety

All public types must be Send + Sync:

// Good: Thread-safe
pub struct MyAgent {
    name: String,
    tools: Vec<Arc<dyn Tool>>,  // Arc for shared ownership
}

// Verify with compile-time checks
fn assert_send_sync<T: Send + Sync>() {}
fn _check() {
    assert_send_sync::<MyAgent>();
}

Testing

Test Organization

crate/
├── src/
│   ├── lib.rs          # Unit tests at bottom of file
│   └── module.rs       # Module-specific tests
└── tests/
    └── integration.rs  # Integration tests

Unit Tests

Place unit tests in the same file as the code:

pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_add() {
        assert_eq!(add(2, 3), 5);
    }

    #[tokio::test]
    async fn test_async_function() {
        let result = async_function().await;
        assert!(result.is_ok());
    }
}

Integration Tests

Place in tests/ directory:

// tests/integration_test.rs
use adk_core::*;

#[tokio::test]
async fn test_full_workflow() {
    // Setup
    let service = InMemorySessionService::new();

    // Execute
    let session = service.create(request).await.unwrap();

    // Assert
    assert_eq!(session.id(), "test-session");
}

Mock Testing

Use MockLlm for testing without API calls:

use adk_model::MockLlm;

#[tokio::test]
async fn test_agent_with_mock() {
    let mock = MockLlm::new(vec![
        "First response".to_string(),
        "Second response".to_string(),
    ]);

    let agent = LlmAgentBuilder::new("test")
        .model(Arc::new(mock))
        .build()
        .unwrap();

    // Test agent behavior
}

Test Commands

# Run all tests
cargo test --all

# Run specific crate tests
cargo test --package adk-core

# Run with output
cargo test --all -- --nocapture

# Run ignored tests (require API keys)
cargo test --all -- --ignored

Documentation

Doc Comments

Use /// for public items:

/// Creates a new LLM agent with the specified configuration.
///
/// # Arguments
///
/// * `name` - A unique identifier for this agent
/// * `model` - The LLM provider to use for reasoning
///
/// # Examples
///
/// ```rust
/// use adk_agent::LlmAgentBuilder;
///
/// let agent = LlmAgentBuilder::new("assistant")
///     .model(Arc::new(model))
///     .build()?;
/// ```
///
/// # Errors
///
/// Returns `AdkError::Agent` if the model is not set.
pub fn new(name: impl Into<String>) -> Self {
    // ...
}

Module Documentation

Add module-level docs at the top of lib.rs:

//! # adk-core
//!
//! Core types and traits for ADK-Rust.
//!
//! ## Overview
//!
//! This crate provides the foundational types...

README Files

Each crate should have a README.md with:

1. Brief description
2. Installation instructions
3. Quick example
4. Link to full documentation

Documentation Tests

Ensure doc examples compile:

cargo test --doc --all

Pull Request Process

Before Submitting

1. Run the full test suite:

   cargo test --all

2. Run clippy:

   cargo clippy --all-targets --all-features

3. Format code:

   cargo fmt --all

4. Update documentation if adding/changing public API

5. Add tests for new functionality

PR Guidelines

• Title: Clear, concise description of the change
• Description: Explain what and why (not how)
• Size: Keep PRs focused; split large changes
• Tests: Include tests for new functionality
• Breaking changes: Clearly document in description

Commit Messages

Follow conventional commits:

feat: add OpenAI streaming support
fix: correct tool parameter validation
docs: update quickstart guide
refactor: simplify session state management
test: add integration tests for A2A protocol

Common Tasks

Adding a New Tool

1. Create the tool:

use adk_core::{Tool, ToolContext, Result};
use async_trait::async_trait;
use serde_json::Value;

pub struct MyTool {
    // fields
}

#[async_trait]
impl Tool for MyTool {
    fn name(&self) -> &str {
        "my_tool"
    }

    fn description(&self) -> &str {
        "Does something useful"
    }

    fn parameters_schema(&self) -> Option<Value> {
        Some(serde_json::json!({
            "type": "object",
            "properties": {
                "input": { "type": "string" }
            },
            "required": ["input"]
        }))
    }

    async fn execute(&self, ctx: Arc<dyn ToolContext>, args: Value) -> Result<Value> {
        let input = args["input"].as_str().unwrap_or_default();
        Ok(serde_json::json!({ "result": input }))
    }
}

1. Add to agent:

let agent = LlmAgentBuilder::new("agent")
    .model(model)
    .tool(Arc::new(MyTool::new()))
    .build()?;

Adding a New Model Provider

1. Create module in adk-model/src/:

// adk-model/src/mymodel/mod.rs
mod client;
pub use client::MyModelClient;

1. Implement the Llm trait:

use adk_core::{Llm, LlmRequest, LlmResponse, LlmResponseStream, Result};

pub struct MyModelClient {
    api_key: String,
}

#[async_trait]
impl Llm for MyModelClient {
    fn name(&self) -> &str {
        "my-model"
    }

    async fn generate_content(
        &self,
        request: LlmRequest,
        stream: bool,
    ) -> Result<LlmResponseStream> {
        // Implementation
    }
}

1. Add feature flag in adk-model/Cargo.toml:

[features]
mymodel = ["dep:mymodel-sdk"]

1. Export conditionally:

#[cfg(feature = "mymodel")]
pub mod mymodel;
#[cfg(feature = "mymodel")]
pub use mymodel::MyModelClient;

Adding a New Agent Type

1. Create module in adk-agent/src/:

// adk-agent/src/my_agent.rs
use adk_core::{Agent, EventStream, InvocationContext, Result};
use async_trait::async_trait;

pub struct MyAgent {
    name: String,
}

#[async_trait]
impl Agent for MyAgent {
    fn name(&self) -> &str {
        &self.name
    }

    fn description(&self) -> &str {
        "My custom agent"
    }

    async fn run(&self, ctx: Arc<dyn InvocationContext>) -> Result<EventStream> {
        // Implementation
    }
}

1. Export in adk-agent/src/lib.rs:

mod my_agent;
pub use my_agent::MyAgent;

Debugging Tips

1. Enable tracing:

   adk_telemetry::init_telemetry();

2. Inspect events:

   while let Some(event) = stream.next().await {
       eprintln!("Event: {:?}", event);
   }

3. Use RUST_LOG:

   RUST_LOG=debug cargo run --example myexample

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