> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mcpblacksmith.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Security Features

> Circuit breakers, rate limiting, retries, timeouts, and validation — built into every generated server.

## Overview

Every generated MCP server includes multiple layers of resilience and security, protecting both the AI agent and the target API. All features are configurable via the `.env` file.

## Retry with exponential backoff

Failed requests are automatically retried with increasing delays:

| Attempt | Delay       |
| ------- | ----------- |
| 1st     | Immediate   |
| 2nd     | \~2 seconds |
| 3rd     | \~4 seconds |

Retries are triggered on transient errors: HTTP 429 (rate limited), 500, 502, 503, and 504.

```bash .env theme={null}
MAX_RETRIES=3
RETRY_BACKOFF_FACTOR=2.0
```

Set `MAX_RETRIES=0` to disable retries.

## Circuit breaker

Prevents cascading failures when the target API is down. Instead of repeatedly hitting a failing endpoint, the circuit breaker temporarily blocks requests and returns an error immediately.

**States:**

* **Closed** (normal) — Requests pass through. Failures are counted.
* **Open** (blocking) — Requests are blocked immediately. Entered after consecutive failures exceed the threshold.
* **Half-open** (testing) — After a timeout, a limited number of requests are allowed through to test recovery.

```bash .env theme={null}
CIRCUIT_BREAKER_FAILURE_THRESHOLD=5
CIRCUIT_BREAKER_TIMEOUT_SECONDS=60
```

## Rate limiting

Prevents your server from overwhelming the target API.

Uses a **token bucket** algorithm — requests consume tokens, tokens regenerate at a configured rate. When the bucket is empty, requests are delayed.

```bash .env theme={null}
RATE_LIMIT_REQUESTS_PER_SECOND=10
```

## Timeouts

Multi-layer timeout configuration prevents hanging requests:

```bash .env theme={null}
# Individual HTTP phases
HTTPX_CONNECT_TIMEOUT=10.0       # Connection establishment
HTTPX_READ_TIMEOUT=60.0          # Waiting for response
HTTPX_WRITE_TIMEOUT=30.0         # Sending request body
HTTPX_POOL_TIMEOUT=5.0           # Acquiring connection from pool

# Overall tool execution
TOOL_EXECUTION_TIMEOUT=90.0      # Total time for one tool call
```

## Connection pool

HTTP connections are reused for efficiency:

```bash .env theme={null}
CONNECTION_POOL_SIZE=100
MAX_KEEPALIVE_CONNECTIONS=20
```

Cookies are disabled across requests for safety in multi-tenant scenarios.

## Input validation

All request parameters are validated using Pydantic models before any HTTP request is made:

* **Type checking** — Correct types enforced (string, integer, boolean, etc.)
* **Required fields** — Missing required parameters are rejected with clear error messages
* **Format validation** — Dates, emails, UUIDs, IP addresses validated against [50+ formats](/reference/oas-3-0#extended-formats) (full OAS Format Registry coverage)
* **Strict mode** — Unknown/extra fields are rejected

## Response validation

Optionally validate API responses against the OpenAPI [response schema](/reference/oas-3-0#responses):

```bash .env theme={null}
RESPONSE_VALIDATION_MODE=warn    # off, warn, or strict
```

| Mode     | Behavior                                                                 |
| -------- | ------------------------------------------------------------------------ |
| `off`    | No response validation (fastest)                                         |
| `warn`   | Validate and log warnings, but return data anyway (default)              |
| `strict` | Block invalid responses — returns error if response doesn't match schema |

## Response sanitization

Optionally redact sensitive fields from API responses before returning them to the AI agent:

```bash .env theme={null}
SANITIZATION_LEVEL=DISABLED      # DISABLED, LOW, MEDIUM, or HIGH
```

| Level  | Fields redacted                                   |
| ------ | ------------------------------------------------- |
| LOW    | `password`, `token`, `secret`, `private_key`      |
| MEDIUM | + `access_token`, `credentials`, `authorization`  |
| HIGH   | + `session_id`, `cookie`, `api_key`, `ip_address` |