max-params.md

llm-core/max-params

📝 Enforce a maximum number of function parameters to encourage object parameter patterns.

💼 This rule is enabled in the following configs: 🌐 all, 🧮 complexity, ✅ recommended.

Enforce a maximum number of function parameters to encourage object parameter patterns.

Rule Details

LLMs frequently generate functions with many positional parameters. This makes function calls error-prone — parameter order is easy to confuse, and adding new parameters requires updating every call site.

This rule limits function parameters (default: 2) and encourages using a single options object with destructuring instead.

Constructors have a separate, higher limit (default: 5) to accommodate dependency injection patterns.

Examples

Incorrect

// Too many positional parameters
function fetchAttachment(
  url: string,
  logger: Logger,
  maxSizeBytes: number,
  timeoutMs: number,
  allowedDomains: string[],
  regulationId: string,
) {
  // ...
}

Correct

// Object parameter with destructuring
type FetchOptions = {
  url: string;
  logger: Logger;
  maxSizeBytes: number;
  timeoutMs: number;
  allowedDomains: string[];
  regulationId: string;
};

function fetchAttachment(options: FetchOptions) {
  const { url, logger, maxSizeBytes, timeoutMs, allowedDomains, regulationId } =
    options;
  // ...
}

Options

max

Maximum allowed parameters for functions. Default: 2.

maxConstructor

Maximum allowed parameters for class constructors. Default: 5.

maxInternal

Maximum allowed parameters for non-exported functions. Default: same as max.

This creates a useful tiering: exported functions (public API) are held to the stricter max limit and encouraged to use options objects, while internal helpers like handleError(error, message, context) get a relaxed limit.

{
  "llm-core/max-params": [
    "error",
    {
      "max": 2,
      "maxConstructor": 5,
      "maxInternal": 3
    }
  ]
}

Error Messages

Error messages follow a structured teaching format designed for LLM self-correction:

1. What's wrong — identifies the function and parameter count
2. Why — explains that positional parameters are error-prone
3. How to fix — shows the exact transformation to an options object with the function's actual parameter names