> ## Documentation Index
> Fetch the complete documentation index at: https://docs.leanmcp.com/llms.txt
> Use this file to discover all available pages before exploring further.
# For Developers
> Build AI-powered applications with security, observability, and cost control
# AI Gateway for Developers
If you're building applications that use AI, the AI Gateway provides essential features for production deployments: user management, abuse prevention, cost tracking, and optimization tools.
## Why Developers Need AI Gateway
When you release an AI-powered app to users, you face several challenges:
Users may try to abuse your AI features, running up costs or extracting your prompts
Without limits, a few heavy users can consume your entire AI budget
You can't see how users are actually using your AI features
You don't know which prompts or models perform best
## Key Features for Developers
### 1. User-Level Tracking
Track AI usage per user in your application:
```typescript theme={null}
const response = await client.chat.completions.create({
model: 'gpt-5.2',
messages: [{ role: 'user', content: userMessage }],
}, {
headers: {
'X-User-ID': userId,
'X-Session-ID': sessionId,
}
});
```
This enables:
* **Usage limits per user** - prevent abuse
* **Cost attribution** - know who's using what
* **Behavior analysis** - understand usage patterns
### 2. Abuse Prevention
Protect your application from abuse:
* **Rate limiting** - limit requests per user/minute
* **User blocking** - instantly block abusive users
* **Pattern detection** - identify suspicious usage patterns
* **Cost caps** - set maximum spend per user
```typescript theme={null}
// Block a user via API
await leanmcp.gateway.blockUser({
userId: 'abusive-user-123',
reason: 'Excessive usage detected',
});
```
### 3. Competitor Intelligence
Understand how similar applications use AI:
* **Prompt patterns** - see what prompts work well
* **Model choices** - understand which models others use
* **Token efficiency** - compare your usage to benchmarks
* **Best practices** - learn from successful implementations
### 4. A/B Testing
Test different prompts and models to optimize performance:
```typescript theme={null}
// A/B test different prompts
const variant = await leanmcp.gateway.getVariant({
experimentId: 'prompt-optimization-v1',
userId: userId,
});
const systemPrompt = variant === 'A'
? 'You are a helpful assistant.'
: 'You are an expert software engineer.';
const response = await client.chat.completions.create({
model: 'gpt-5.2',
messages: [
{ role: 'system', content: systemPrompt },
{ role: 'user', content: userMessage }
],
}, {
headers: {
'X-Experiment-ID': 'prompt-optimization-v1',
'X-Variant': variant,
}
});
```
Track and compare:
* **Response quality** - user satisfaction metrics
* **Token usage** - cost per variant
* **Latency** - response time differences
* **Conversion rates** - business impact
## Integration Guide
### Basic Setup
```typescript theme={null}
import OpenAI from 'openai';
const client = new OpenAI({
baseURL: 'https://aigateway.leanmcp.com/v1/openai',
apiKey: process.env.LEANMCP_API_KEY,
});
// All requests now go through the gateway
const response = await client.chat.completions.create({
model: 'gpt-5.2',
messages: [{ role: 'user', content: 'Hello!' }],
});
```
### Adding User Context
```typescript theme={null}
async function generateResponse(userId: string, sessionId: string, message: string) {
return await client.chat.completions.create({
model: 'gpt-5.2',
messages: [{ role: 'user', content: message }],
}, {
headers: {
'X-User-ID': userId,
'X-Session-ID': sessionId,
'X-Request-Source': 'web-app',
}
});
}
```
### Implementing Rate Limits
Set up rate limits in your dashboard or via API:
```typescript theme={null}
// Configure rate limits
await leanmcp.gateway.setRateLimit({
userId: userId,
limits: {
requestsPerMinute: 10,
tokensPerDay: 100000,
maxCostPerMonth: 50.00,
}
});
```
## Dashboard Features
### Usage Analytics
* **Request volume** over time
* **Token usage** by model and user
* **Cost breakdown** by feature and user segment
* **Error rates** and failure analysis
### User Management
* View all users and their usage
* Set individual limits and permissions
* Block or restrict users
* Export usage data
### Alerts & Monitoring
Set up alerts for:
* **Unusual usage spikes**
* **Budget thresholds**
* **Error rate increases**
* **Specific user behaviors**
## Production Best Practices
Include X-User-ID and X-Session-ID to enable per-user tracking and limits.
Configure maximum spend limits before launch to prevent surprises.
Watch your dashboard closely during launch to catch abuse early.
Continuously optimize your prompts and model choices with experiments.
Regularly check what's being blocked to tune your security rules.
## API Reference
Full API documentation for gateway management:
```typescript theme={null}
// Gateway Management API
leanmcp.gateway.blockUser({ userId, reason })
leanmcp.gateway.unblockUser({ userId })
leanmcp.gateway.setRateLimit({ userId, limits })
leanmcp.gateway.getUsage({ userId, dateRange })
leanmcp.gateway.getVariant({ experimentId, userId })
leanmcp.gateway.recordOutcome({ experimentId, userId, outcome })
```
## Next Steps
Advanced security and blocking rules
Reduce costs and improve efficiency
Complete code examples for all providers
Deep dive into logging and monitoring
***
View your first logged AI request at **app.leanmcp.com/observability**