# How deepwiki-mcp Enforces Domain-Restricted Crawling Security

> Learn how deepwiki-mcp enforces domain-restricted crawling security by validating URLs against deepwiki.com, preventing unauthorized access. Discover the strict whitelist mechanism.

- Repository: [Kevin Kern/deepwiki-mcp](https://github.com/regenrek/deepwiki-mcp)
- Tags: security
- Published: 2026-02-16

---

**The deepwiki-mcp tool implements a strict domain whitelist by validating the target URL hostname against `deepwiki.com` after normalization, rejecting any non-matching requests with a `DOMAIN_NOT_ALLOWED` error.**

The deepwiki-mcp repository provides a Model Context Protocol (MCP) tool designed specifically for crawling documentation from deepwiki.com. To prevent accidental or malicious cross-site crawling, the implementation incorporates multiple **deepwiki-mcp crawling security** layers that enforce strict domain restrictions through runtime validation, schema enforcement, and comprehensive test coverage.

## URL Normalization and Input Processing

Before any security checks execute, the tool normalizes user input to ensure consistent URL formatting. Located in **src/tools/deepwiki.ts** (lines 20‑69), this preprocessing logic converts shorthand inputs—such as `owner/repo` strings or keyword shortcuts—into fully qualified `https://deepwiki.com/...` URLs.

This normalization step is critical for **deepwiki-mcp domain restriction** enforcement because it ensures the subsequent security validation operates on a standardized `URL` object rather than raw user input that might bypass filters through encoding variations or path manipulation.

## Runtime Domain Validation

The core security mechanism resides immediately after normalization in **src/tools/deepwiki.ts** (lines 96‑101). Once the tool instantiates a `URL` object (`root`), it performs an explicit hostname check:

```typescript
if (root.hostname !== 'deepwiki.com') {
  const err: z.infer<typeof ErrorEnvelope> = {
    status: 'error',
    code: 'DOMAIN_NOT_ALLOWED',
    message: 'Only deepwiki.com domains are allowed',
  }
  return err
}

```

This runtime validation guarantees that **deepwiki-mcp crawling security** cannot be circumvented through URL redirection, DNS spoofing attempts, or user input errors. Any hostname other than exactly `deepwiki.com` triggers an immediate `ErrorEnvelope` response with the code `DOMAIN_NOT_ALLOWED`, preventing the HTTP crawler from ever executing the request.

## Schema and Type Safety

While runtime validation provides the primary defense, the tool also employs schema-level constraints defined in **src/schemas/deepwiki.ts**. The `FetchRequest` schema enforces that the `url` parameter must be a string, ensuring type safety before the domain-specific logic executes.

However, the actual **deepwiki-mcp domain restriction** logic remains intentionally implemented in the runtime check rather than the schema, allowing for more descriptive error messages and flexible URL normalization preprocessing.

## Test Coverage and Verification

The security implementation includes comprehensive validation through unit tests located in **tests/client.test.ts**. These tests verify that:

- Valid `deepwiki.com` URLs proceed through the tool successfully
- Any non-`deepwiki.com` domain returns the expected `DOMAIN_NOT_ALLOWED` error

This test coverage ensures that **deepwiki-mcp crawling security** measures remain functional across code updates and dependency changes, preventing regression in domain restriction behavior.

## Summary

The deepwiki-mcp tool implements a defense-in-depth strategy for **deepwiki-mcp crawling security**:

- **URL normalization** in [`src/tools/deepwiki.ts`](https://github.com/regenrek/deepwiki-mcp/blob/main/src/tools/deepwiki.ts) standardizes inputs before validation
- **Runtime domain checking** explicitly validates the `hostname` property against `deepwiki.com`, rejecting all other domains with a `DOMAIN_NOT_ALLOWED` error
- **Schema enforcement** provides type safety for request parameters
- **Unit tests** verify the restriction logic prevents cross-site crawling attempts

These measures collectively ensure the MCP tool can only access resources from the intended deepwiki.com domain.

## Frequently Asked Questions

### How does deepwiki-mcp prevent crawling external websites?

The tool enforces a strict whitelist by inspecting the `hostname` property of the normalized URL object. If the hostname does not exactly match `deepwiki.com`, the tool immediately returns an `ErrorEnvelope` with code `DOMAIN_NOT_ALLOWED` and never initiates the HTTP request. This check occurs in [`src/tools/deepwiki.ts`](https://github.com/regenrek/deepwiki-mcp/blob/main/src/tools/deepwiki.ts) after URL normalization but before any network activity.

### Can users bypass the domain restriction using URL encoding or IP addresses?

No. The security check uses the parsed `URL` object’s `hostname` property, which automatically decodes percent-encoded characters and resolves IP addresses to their canonical hostnames. Since the validation occurs after normalization in [`src/tools/deepwiki.ts`](https://github.com/regenrek/deepwiki-mcp/blob/main/src/tools/deepwiki.ts) (lines 96‑101), attempts to bypass restrictions through encoding tricks, punycode, or direct IP access are normalized and then rejected if they do not resolve to exactly `deepwiki.com`.

### What error message does deepwiki-mcp return for invalid domains?

When a request targets any domain other than `deepwiki.com`, the tool returns a structured error object conforming to the `ErrorEnvelope` schema defined in [`src/schemas/deepwiki.ts`](https://github.com/regenrek/deepwiki-mcp/blob/main/src/schemas/deepwiki.ts). The response contains `status: 'error'`, `code: 'DOMAIN_NOT_ALLOWED'`, and the message `"Only deepwiki.com domains are allowed"`. This standardized error format allows MCP clients to programmatically detect and handle domain restriction violations.

### Where is the domain whitelist logic tested?

The domain restriction is validated through unit tests in **tests/client.test.ts**. These tests confirm that the tool accepts valid `deepwiki.com` URLs while rejecting external domains with the appropriate `DOMAIN_NOT_ALLOWED` error code. This test coverage ensures the security logic remains intact across code updates and dependency changes.