OpenRouter API Client Library

A production-ready Rust client for the OpenRouter API with comprehensive security, ergonomic design, and extensive testing. The library uses a type‑state builder pattern for compile-time configuration validation, ensuring robust and secure API interactions.

Features

🏗️ Architecture & Safety

• Type‑State Builder Pattern: Compile-time configuration validation ensures all required settings are provided before making requests
• Secure Memory Management: API keys are automatically zeroed on drop using the zeroize crate for enhanced security
• Comprehensive Error Handling: Centralized error management with safe error message redaction to prevent sensitive data leakage
• Modular Organization: Clean separation of concerns across modules for models, API endpoints, types, and utilities

🚀 Ergonomic API Design

• Convenient Constructors: Quick setup with from_api_key(), from_env(), quick(), and production() methods
• Flexible Configuration: Fluent builder pattern with timeout, retry, and header configuration
• Environment Integration: Automatic API key loading from OPENROUTER_API_KEY or OR_API_KEY environment variables

🔒 Security & Reliability

• Memory Safety: Secure API key handling with automatic memory zeroing
• Response Redaction: Automatic sanitization of error messages to prevent sensitive data exposure
• Streaming Safety: Buffer limits and backpressure handling for streaming responses
• Input Validation: Comprehensive validation of requests and parameters

🌐 OpenRouter API Support

• Chat Completions: Full support for OpenRouter's chat completion API with streaming
• Text Completions: Traditional text completion endpoint with customizable parameters
• Tool Calling: Define and invoke function tools with proper validation
• Structured Outputs: JSON Schema validation for structured response formats
• Web Search: Type-safe web search API integration
• Provider Preferences: Configure model routing, fallbacks, and provider selection

📡 Model Context Protocol (MCP)

• MCP Client: Full JSON-RPC client implementation for the Model Context Protocol
• Resource Access: Retrieve resources from MCP servers
• Tool Invocation: Execute tools provided by MCP servers
• Context Integration: Seamless context sharing between applications and LLMs

🧪 Quality & Testing

• 100% Test Coverage: Comprehensive unit and integration test suite
• CI/CD Pipeline: Automated quality gates with formatting, linting, security audits, and documentation checks
• Production Ready: Extensive error handling, retry logic, and timeout management

Getting Started

Installation

Add the following to your project's Cargo.toml:

cargo add openrouter_api

# With optional tracing support for better error logging
cargo add openrouter_api --features tracing

Available Features:

• rustls (default): Use rustls for TLS
• native-tls: Use system TLS
• tracing: Enhanced error logging with tracing support

Ensure that you have Rust installed (tested with Rust v1.83.0) and that you're using Cargo for building and testing.

Quick Start Examples

Simple Chat Completion

use openrouter_api::{OpenRouterClient, Result};
use openrouter_api::types::chat::{ChatCompletionRequest, Message};

#[tokio::main]
async fn main() -> Result<()> {
    // Quick setup from environment variable (OPENROUTER_API_KEY)
    let client = OpenRouterClient::from_env()?;
    
    // Or directly from API key
    // let client = OpenRouterClient::from_api_key("sk-or-v1-...")?;

    let request = ChatCompletionRequest {
        model: "openai/gpt-4o".to_string(),
        messages: vec![Message {
            role: "user".to_string(),
            content: "Hello, world!".to_string(),
            name: None,
            tool_calls: None,
        }],
        stream: None,
        response_format: None,
        tools: None,
        provider: None,
        models: None,
        transforms: None,
    };

    let response = client.chat()?.chat_completion(request).await?;
    
    if let Some(choice) = response.choices.first() {
        println!("Response: {}", choice.message.content);
    }
    Ok(())
}

Production Configuration

use openrouter_api::{OpenRouterClient, Result};

#[tokio::main]
async fn main() -> Result<()> {
    // Production-ready client with optimized settings
    let client = OpenRouterClient::production(
        "sk-or-v1-...",           // API key
        "My Production App",       // App name
        "https://myapp.com"       // App URL
    )?;
    
    // Client is now configured with:
    // - 60 second timeout
    // - 5 retries with exponential backoff
    // - Proper headers for app identification
    
    // Use the client...
    Ok(())
}

Custom Configuration

use openrouter_api::{OpenRouterClient, Result};
use std::time::Duration;

#[tokio::main]
async fn main() -> Result<()> {
    // Full control over client configuration
    let client = OpenRouterClient::new()
        .skip_url_configuration()  // Use default OpenRouter URL
        .with_timeout_secs(120)    // 2-minute timeout
        .with_retries(3, 500)      // 3 retries, 500ms initial backoff
        .with_http_referer("https://myapp.com")
        .with_site_title("My Application")
        .with_api_key("sk-or-v1-...")?;
    
    // Ready to use
    Ok(())
}

Provider Preferences Example

use openrouter_api::{OpenRouterClient, utils, Result};
use openrouter_api::models::provider_preferences::{DataCollection, ProviderPreferences, ProviderSort};
use openrouter_api::types::chat::{ChatCompletionRequest, Message};
use serde_json::json;

#[tokio::main]
async fn main() -> Result<()> {
    // Load API key from environment variables
    let api_key = utils::load_api_key_from_env()?;

    // Build the client
    let client = OpenRouterClient::new()
        .with_base_url("https://openrouter.ai/api/v1/")?
        .with_api_key(api_key)?;
    
    // Create provider preferences
    let preferences = ProviderPreferences::new()
        .with_order(vec!["OpenAI".to_string(), "Anthropic".to_string()])
        .with_allow_fallbacks(true)
        .with_data_collection(DataCollection::Deny)
        .with_sort(ProviderSort::Throughput);
    
    // Create a request builder with provider preferences
    let request_builder = client.chat_request_builder(vec![
        Message {
            role: "user".to_string(),
            content: "Hello with provider preferences!".to_string(),
            name: None,
            tool_calls: None,
        },
    ]);
    
    // Add provider preferences and build the payload
    let payload = request_builder
        .with_provider_preferences(preferences)?
        .build();
    
    // The payload now includes provider preferences!
    println!("Request payload: {}", serde_json::to_string_pretty(&payload)?);
    
    Ok(())
}

Model Context Protocol (MCP) Client Example

use openrouter_api::{MCPClient, Result};
use openrouter_api::mcp_types::{
    ClientCapabilities, GetResourceParams, ToolCallParams,
    MCP_PROTOCOL_VERSION
};

#[tokio::main]
async fn main() -> Result<()> {
    // Create a new MCP client
    let client = MCPClient::new("https://mcp-server.example.com/mcp")?;
    
    // Initialize the client with client capabilities
    let server_capabilities = client.initialize(ClientCapabilities {
        protocolVersion: MCP_PROTOCOL_VERSION.to_string(),
        supportsSampling: Some(true),
    }).await?;
    
    println!("Connected to MCP server with capabilities: {:?}", server_capabilities);
    
    // Get a resource from the MCP server
    let resource = client.get_resource(GetResourceParams {
        id: "document-123".to_string(),
        parameters: None,
    }).await?;
    
    println!("Retrieved resource: {}", resource.content);
    
    // Call a tool on the MCP server
    let result = client.tool_call(ToolCallParams {
        id: "search-tool".to_string(),
        parameters: serde_json::json!({
            "query": "Rust programming"
        }),
    }).await?;
    
    println!("Tool call result: {:?}", result.result);
    
    Ok(())
}

Text Completion Example

use openrouter_api::{OpenRouterClient, utils, Result};
use openrouter_api::types::completion::CompletionRequest;
use serde_json::json;

#[tokio::main]
async fn main() -> Result<()> {
    // Load API key from environment
    let api_key = utils::load_api_key_from_env()?;

    // Build the client
    let client = OpenRouterClient::new()
        .with_base_url("https://openrouter.ai/api/v1/")?
        .with_api_key(api_key)?;

    // Create a text completion request
    let request = CompletionRequest {
        model: "openai/gpt-3.5-turbo-instruct".to_string(),
        prompt: "Once upon a time".to_string(),
        // Additional generation parameters
        extra_params: json!({
            "temperature": 0.8,
            "max_tokens": 50
        }),
    };

    // Invoke the text completion endpoint
    let completions_api = client.completions()?;
    let response = completions_api.text_completion(request).await?;

    // Print out the generated text
    if let Some(choice) = response.choices.first() {
        println!("Text Completion: {}", choice.text);
    }
    Ok(())
}

Streaming Chat Example

use openrouter_api::{OpenRouterClient, utils, Result};
use openrouter_api::types::chat::{ChatCompletionRequest, Message};
use futures::StreamExt;
use std::io::Write;

#[tokio::main]
async fn main() -> Result<()> {
    // Load API key from environment
    let api_key = utils::load_api_key_from_env()?;

    // Build the client
    let client = OpenRouterClient::new()
        .with_base_url("https://openrouter.ai/api/v1/")?
        .with_api_key(api_key)?;

    // Create a chat completion request with streaming enabled
    let request = ChatCompletionRequest {
        model: "openai/gpt-4o".to_string(),
        messages: vec![Message {
            role: "user".to_string(),
            content: "Tell me a story.".to_string(),
            name: None,
            tool_calls: None,
        }],
        stream: Some(true),
        response_format: None,
        tools: None,
        provider: None,
        models: None,
        transforms: None,
    };

    // Invoke the streaming chat completion endpoint
    let chat_api = client.chat()?;
    let mut stream = chat_api.chat_completion_stream(request);

    // Process the stream - accumulating content and tracking usage
    let mut total_content = String::new();
    while let Some(chunk) = stream.next().await {
        match chunk {
            Ok(c) => {
                if let Some(choice) = c.choices.first() {
                    if let Some(content) = &choice.delta.content {
                        print!("{}", content);
                        total_content.push_str(content);
                        std::io::stdout().flush().unwrap();
                    }
                }
                
                // Check for usage information in final chunk
                if let Some(usage) = c.usage {
                    println!("\nUsage: {} prompt + {} completion = {} total tokens", 
                        usage.prompt_tokens, usage.completion_tokens, usage.total_tokens);
                }
            },
            Err(e) => eprintln!("Error during streaming: {}", e),
        }
    }
    println!();
    Ok(())
}

Model Context Protocol (MCP) Client

The library includes a client implementation for the Model Context Protocol, which is an open protocol that standardizes how applications provide context to LLMs.

Key features of the MCP client include:

• JSON-RPC Communication: Implements the JSON-RPC 2.0 protocol for MCP
• Resource Access: Retrieve resources from MCP servers
• Tool Invocation: Call tools provided by MCP servers
• Prompt Execution: Execute prompts on MCP servers
• Server Capabilities: Discover and leverage server capabilities
• Proper Authentication: Handle initialization and authentication flows

// Create an MCP client connected to a server
let client = MCPClient::new("https://mcp-server.example.com/mcp")?;

// Initialize with client capabilities
let server_capabilities = client.initialize(ClientCapabilities {
    protocolVersion: "2025-03-26".to_string(),
    supportsSampling: Some(true),
}).await?;

// Access resources from the server
let resource = client.get_resource(GetResourceParams {
    id: "some-resource-id".to_string(),
    parameters: None,
}).await?;

See the Model Context Protocol specification for more details.

Implementation Status

This is a production-ready library with comprehensive functionality:

✅ Core Features (Completed)

• Client Framework: Type‑state builder pattern with compile‑time validation
• Security: Secure API key handling with memory zeroing and error redaction
• Chat Completions: Full OpenRouter chat API support with streaming
• Text Completions: Traditional text completion endpoint
• Web Search: Integrated web search capabilities
• Tool Calling: Function calling with validation
• Structured Outputs: JSON Schema validation
• Provider Preferences: Model routing and fallback configuration
• Model Context Protocol: Complete MCP client implementation

✅ Quality Infrastructure (Completed)

• 100% Test Coverage: 80+ comprehensive unit and integration tests
• Security Auditing: Automated security vulnerability scanning
• CI/CD Pipeline: GitHub Actions with quality gates
• Documentation: Complete API documentation with examples
• Developer Experience: Contributing guidelines, issue templates, PR templates

✅ Ergonomic Improvements (Completed)

• Convenience Constructors: from_env(), from_api_key(), production(), quick()
• Flexible Configuration: Timeout, retry, and header management
• Error Handling: Comprehensive error types with context
• Memory Safety: Automatic sensitive data cleanup

🔄 Future Enhancements

• Models Listing: Endpoint to list available models
• Credits API: Account credit and usage tracking
• Performance Optimizations: Connection pooling and caching
• Extended MCP Features: Additional MCP protocol capabilities

Contributing

Contributions are welcome! Please open an issue or submit a pull request with your ideas or fixes. Follow the code style guidelines and ensure that all tests pass.

License

Distributed under either the MIT license or the Apache License, Version 2.0. See LICENSE for details.

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OpenRouter API Rust Crate Documentation

Version: 0.1.6 • License: MIT / Apache‑2.0

The openrouter_api crate is a comprehensive client for interacting with the OpenRouter API and Model Context Protocol servers. It provides strongly‑typed endpoints for chat completions, text completions, web search, and MCP connections. The crate is built using asynchronous Rust and leverages advanced patterns for safe and flexible API usage.

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Table of Contents

• Core Concepts
• Installation
• Architecture & Module Overview
• Client Setup & Type‑State Pattern
• API Endpoints
  • Chat Completions
  • Text Completions
  • Web Search
  • Tool Calling & Structured Output
  • Model Context Protocol
• Error Handling
• Best Practices
• Examples
• Additional Resources

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Core Concepts

• Type‑State Client Configuration: The client is built using a type‑state pattern to ensure that required parameters are set before making any API calls.

• Provider Preferences: Strongly-typed configuration for model routing, fallbacks, and provider selection.

• Asynchronous Streaming: Support for streaming responses via asynchronous streams.

• Model Context Protocol: Client implementation for connecting to MCP servers to access resources, tools, and prompts.

• Error Handling & Validation: Comprehensive error handling with detailed context and validation utilities.

---

Architecture & Module Overview

The crate is organized into several modules:

• client: Type-state client implementation with builder pattern
• api: API endpoint implementations (chat, completions, web search, etc.)
• models: Domain models for structured outputs, provider preferences, tools
• types: Type definitions for requests and responses
• mcp: Model Context Protocol client implementation
• error: Centralized error handling
• utils: Utility functions and helpers

---

Client Setup & Type‑State Pattern

// Quick setup (recommended for most use cases)
let client = OpenRouterClient::from_env()?;

// Production setup with optimized settings
let client = OpenRouterClient::production(
    "sk-or-v1-...",
    "My App", 
    "https://myapp.com"
)?;

// Full control with type-state pattern
let client = OpenRouterClient::new()
    .with_base_url("https://openrouter.ai/api/v1/")?
    .with_timeout(Duration::from_secs(30))
    .with_http_referer("https://your-app.com/")
    .with_api_key(std::env::var("OPENROUTER_API_KEY")?)?;

API Endpoints

Chat Completions

// Basic chat completion
let response = client.chat()?.chat_completion(
    ChatCompletionRequest {
        model: "openai/gpt-4o".to_string(),
        messages: vec![Message {
            role: "user".to_string(),
            content: "Explain quantum computing".to_string(),
            name: None,
            tool_calls: None,
        }],
        stream: None,
        response_format: None,
        tools: None,
        provider: None,
        models: None,
        transforms: None,
    }
).await?;

Tool Calling

// Define a function tool
let weather_tool = Tool::Function { 
    function: FunctionDescription {
        name: "get_weather".to_string(),
        description: Some("Get weather information for a location".to_string()),
        parameters: serde_json::json!({
            "type": "object",
            "properties": {
                "location": {
                    "type": "string",
                    "description": "City and state"
                }
            },
            "required": ["location"]
        }),
    }
};

// Make a request with tool calling enabled
let response = client.chat()?.chat_completion(
    ChatCompletionRequest {
        model: "openai/gpt-4o".to_string(),
        messages: vec![Message {
            role: "user".to_string(),
            content: "What's the weather in Boston?".to_string(),
            name: None,
            tool_calls: None,
        }],
        tools: Some(vec![weather_tool]),
        // other fields...
        stream: None,
        response_format: None,
        provider: None,
        models: None,
        transforms: None,
    }
).await?;

Model Context Protocol

// Create an MCP client
let mcp_client = MCPClient::new("https://mcp-server.example.com/mcp")?;

// Initialize with client capabilities
let server_capabilities = mcp_client.initialize(ClientCapabilities {
    protocolVersion: MCP_PROTOCOL_VERSION.to_string(),
    supportsSampling: Some(true),
}).await?;

// Access a resource from the MCP server
let resource = mcp_client.get_resource(GetResourceParams {
    id: "document-123".to_string(),
    parameters: None,
}).await?;

Error Handling

match client.chat()?.chat_completion(request).await {
    Ok(response) => {
        println!("Success: {}", response.choices[0].message.content);
    },
    Err(e) => match e {
        Error::ApiError { code, message, .. } => {
            eprintln!("API Error ({}): {}", code, message);
        },
        Error::HttpError(ref err) if err.is_timeout() => {
            eprintln!("Request timed out!");
        },
        Error::ConfigError(msg) => {
            eprintln!("Configuration error: {}", msg);
        },
        _ => eprintln!("Other error: {:?}", e),
    }
}

Best Practices

1. Use the Type‑State Pattern: Let the compiler ensure your client is properly configured.

2. Set Appropriate Timeouts & Headers: Configure reasonable timeouts and identify your application.

3. Handle Errors Appropriately: Implement proper error handling for each error type.

4. Use Provider Preferences: Configure provider routing for optimal model selection.

5. Secure Your API Keys: Store keys in environment variables or secure storage.

Additional Resources

• OpenRouter API Documentation
• Model Context Protocol Specification

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