Security Features - MCP Blacksmith Docs

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.

.env

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.

.env

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.

.env

RATE_LIMIT_REQUESTS_PER_SECOND=10

Timeouts

Multi-layer timeout configuration prevents hanging requests:

.env

# 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:

.env

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 (full OAS Format Registry coverage)
Strict mode — Unknown/extra fields are rejected

Response validation

Optionally validate API responses against the OpenAPI response schema:

.env

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:

.env

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`

​Overview

​Retry with exponential backoff

​Circuit breaker

​Rate limiting

​Timeouts

​Connection pool

​Input validation

​Response validation

​Response sanitization

Overview

Retry with exponential backoff

Circuit breaker

Rate limiting

Timeouts

Connection pool

Input validation

Response validation

Response sanitization