Code Explainer MCP

What is Code Explainer MCP?

Code Explainer MCP is a Cloudflare Worker that analyzes source code snippets and returns a Markdown report containing an ASCII architecture diagram, a core-functionality summary, and a breakdown of main classes and functions. It uses only regex and pattern matching—no LLM calls or external dependencies—and supports JavaScript, TypeScript, Python, Java, and C# with a generic fallback.

How to use Code Explainer MCP?

Deploy the Worker to Cloudflare, set the SHARED_SECRET secret, then send a POST request to the Worker URL with a JSON body containing "method": "explainCode" and "params": [code, language]. Include the bearer token in the Authorization: Bearer <SHARED_SECRET> header. For local development, run npm run dev after setting the secret in .dev.vars.

Key features of Code Explainer MCP

• Generates ASCII architecture diagrams showing classes, functions, and call relationships.
• Infers primary and secondary code purpose from weighted pattern matches.
• Extracts main components with descriptions, reusing existing doc comments when available.
• Supports JavaScript, TypeScript, Python, Java, C#, and a generic fallback.
• Bearer-token authentication with constant-time comparison; fails closed if unconfigured.
• Runs entirely inside Cloudflare Workers with no external runtime dependencies.

Use cases of Code Explainer MCP

• Quickly understand an unfamiliar codebase or snippet without an LLM.
• Auto-generate documentation for small to medium code modules.
• Provide architecture summaries in code review or onboarding contexts.
• Enable programmatic code analysis in CI pipelines with a lightweight HTTP endpoint.

FAQ from Code Explainer MCP

Does Code Explainer MCP use an LLM?

No. All analysis is done with regex and pattern matching inside the Worker, with no LLM calls and no external runtime dependencies.

What is the maximum code length accepted?

The code string (params[0]) must not exceed 100,000 characters; longer input is rejected with a 413 status.

Does Code Explainer MCP implement the MCP wire protocol?

No. Despite its name, the current version serves a plain HTTP JSON endpoint with a custom { method, params } body. It does not use workers-mcp at runtime or implement JSON-RPC.

How is authentication handled?

The POST endpoint is protected by a bearer token (SHARED_SECRET) sent in the Authorization header. The Worker fails closed—returning 503 if the secret is unset or still the placeholder—and compares digests in constant time.

What are the prerequisites for development?

Node.js 22 or higher, Wrangler (included in devDependencies), and a Cloudflare account. The Worker is deployed to Cloudflare Workers and tested with Vitest and @cloudflare/vitest-pool-workers.