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).
76
66%
Does it follow best practices?
Impact
88%
1.60xAverage score across 3 eval scenarios
Advisory
Suggest reviewing before use
Optimize this skill with Tessl
npx tessl skill review --optimize ./mcp-builder/SKILL.mdQuality
Discovery
89%Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.
This is a solid description that clearly identifies its niche (MCP server development) and provides explicit 'Use when' guidance with framework-specific triggers. Its main weakness is that it could be more specific about the concrete actions it covers (e.g., defining tools, handling resources, configuring transport) rather than staying at the high-level 'creating servers' framing.
Suggestions
Add more specific concrete actions the skill covers, e.g., 'defining tools and resources, handling authentication, configuring transport layers, structuring server code' to improve specificity.
| Dimension | Reasoning | Score |
|---|---|---|
Specificity | Names the domain (MCP servers) and a general action ('creating high-quality MCP servers that enable LLMs to interact with external services through well-designed tools'), but doesn't list multiple specific concrete actions like defining tools, handling authentication, setting up transport layers, etc. | 2 / 3 |
Completeness | Clearly answers both 'what' (creating high-quality MCP servers that enable LLMs to interact with external services through well-designed tools) and 'when' (explicitly states 'Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript (MCP SDK)'). | 3 / 3 |
Trigger Term Quality | Includes strong natural keywords users would say: 'MCP', 'Model Context Protocol', 'MCP servers', 'FastMCP', 'MCP SDK', 'external APIs', 'Python', 'Node/TypeScript', 'tools'. These cover the main variations a developer would use when asking about building MCP servers. | 3 / 3 |
Distinctiveness Conflict Risk | MCP server development is a very specific niche with distinct triggers (MCP, Model Context Protocol, FastMCP, MCP SDK). It's unlikely to conflict with general coding skills or other integration-related skills. | 3 / 3 |
Total | 11 / 12 Passed |
Implementation
42%Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.
This skill has excellent structure and progressive disclosure, organizing a complex multi-phase workflow with clear references to supporting documents. However, it is significantly too verbose—repeating file references, explaining obvious concepts, and using filler language throughout. The actionability suffers because nearly all concrete implementation details are deferred to reference files, leaving the main skill as mostly abstract guidance rather than executable instructions.
Suggestions
Cut the content by 40-50%: remove the agent-centric design principles section (1.1) or reduce to a brief bullet list, eliminate repeated references to the same guide files, and remove filler phrases like 'Now that you have a comprehensive plan, begin implementation'.
Add at least one minimal but complete working code example (e.g., a 10-line Python FastMCP server with one tool) directly in the skill body so it's actionable without loading reference files.
Strengthen Phase 3.2 testing with explicit validation-fix-retry loops: e.g., 'Run build → if errors, fix → rebuild → only proceed when build succeeds → run evaluation harness → if failures, iterate on tool implementations'.
Consolidate the 'Reference Files' section at the end with the inline references throughout—currently the same files are listed 3+ times across the document.
| Dimension | Reasoning | Score |
|---|---|---|
Conciseness | The skill is extremely verbose at ~300+ lines, with significant redundancy. It explains concepts Claude already knows (what MCP is, what error handling is, what DRY means), repeats references to the same guide files multiple times across sections, and includes unnecessary framing like 'Now that you have a comprehensive plan' and 'To ensure quality, review the code for'. The agent-centric design principles section (1.1) is largely general software design wisdom that doesn't need to be spelled out. | 1 / 3 |
Actionability | The skill provides some concrete guidance (specific URLs to fetch, XML format for evaluations, tool annotation fields, specific commands like `python -m py_compile` and `npm run build`), but most of the content is high-level direction rather than executable code. There are no complete working code examples for creating an MCP server—actual implementation details are deferred to reference files. The Phase 2 implementation section describes what to do abstractly rather than showing how. | 2 / 3 |
Workflow Clarity | The four-phase workflow is clearly sequenced and logically organized, with numbered sub-steps. However, validation checkpoints are weak—Phase 3.2 mentions testing but the guidance is vague ('verify Python syntax', 'check imports work correctly by reviewing the file'). There's no explicit feedback loop for catching and fixing issues during implementation. The warning about hanging processes is valuable but the recovery path is underspecified. | 2 / 3 |
Progressive Disclosure | The skill effectively uses progressive disclosure with a clear overview structure pointing to well-organized reference files (mcp_best_practices.md, python_mcp_server.md, node_mcp_server.md, evaluation.md) at appropriate points. References are one level deep, clearly signaled with emoji markers, and include brief descriptions of what each file contains. The 'Reference Files' section at the end provides a consolidated navigation index. | 3 / 3 |
Total | 8 / 12 Passed |
Validation
100%Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.
Validation — 11 / 11 Passed
Validation for skill structure
No warnings or errors.
362d354
Table of Contents
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