Design vs Testing · both proven

mcp-builder vs test-driven-development

Both skills were run through Claude twice: once on a fixed brief without the skill, once with it. The briefs differ because each is written for the job the skill claims to do, so compare each skill against its own baseline, then decide which difference matters for your work. They are in different categories, so this is a choice of job, not a head-to-head on the same job.

mcp-builder

Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK).

Category: Design
Source: anthropics/skills
License: Not stated
Proof model: claude-opus-5-5
Brief: “Build an MCP server in TypeScript that gives an agent read access to a team's Linear-style issue tracker through a REST API: tools to search issues, get one issue with comments, and list a project's open issues by priority. Present it as a single HTML page with the full source of each file, the tool schemas, how errors and pagination are handled, and how to run and connect it.”
Skill commit: dbd4588

Without the skillWith mcp-builder

⇆

Without, runWith mcp-builder, run3 independent runs per side, none selected by hand.

Download the with-skill page

test-driven-development

Use when implementing any feature or bugfix, before writing implementation code

Category: Testing
Source: obra/superpowers
License: MIT
Proof model: claude-opus-5-5
Brief: “Implement a function that parses a cron expression (the standard five fields) and returns the next run time after a given date, in TypeScript. Present the work as a single HTML page with two columns: the test file on the left and the implementation on the right, each in a code block, with a short note at the top on the order you did things in and anything you decided not to support.”
Skill commit: bb92a77

Without the skillWith test-driven-development

⇆

Without, runWith test-driven-development, run3 independent runs per side, none selected by hand.

Download the with-skill page

We don’t pick a winner for you: the pages are the evidence. Both proofs can be repeated with the brief, model and commit shown above. See alternatives to mcp-builder or alternatives to test-driven-development.