fastmcp.server.middleware.rate_limiting

Rate limiting middleware for protecting FastMCP servers from abuse.

Classes

RateLimitError ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L15" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Error raised when rate limit is exceeded.

TokenBucketRateLimiter ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L22" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Token bucket implementation for rate limiting.

Methods:

consume ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L38" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

consume(self, tokens: int = 1) -> bool

Try to consume tokens from the bucket.

Args:

• tokens: Number of tokens to consume

Returns:

• True if tokens were available and consumed, False otherwise

SlidingWindowRateLimiter ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L61" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Sliding window rate limiter implementation.

Methods:

is_allowed ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L76" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

is_allowed(self) -> bool

Check if a request is allowed.

RateLimitingMiddleware ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L92" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Middleware that implements rate limiting to prevent server abuse.

Uses a token bucket algorithm by default, allowing for burst traffic while maintaining a sustainable long-term rate.

Methods:

on_request ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L152" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

on_request(self, context: MiddlewareContext, call_next: CallNext) -> Any

Apply rate limiting to requests.

SlidingWindowRateLimitingMiddleware ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L170" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Middleware that implements sliding window rate limiting.

Uses a sliding window approach which provides more precise rate limiting but uses more memory to track individual request timestamps.

Methods:

on_request ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/middleware/rate_limiting.py#L219" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

on_request(self, context: MiddlewareContext, call_next: CallNext) -> Any

Apply sliding window rate limiting to requests.