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).
92
73%
Does it follow best practices?
Impact
94%
2.23xAverage score across 10 eval scenarios
Advisory
Suggest reviewing before use
Optimize this skill with Tessl
npx tessl skill review --optimize ./skills/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, configuring transports, handling authentication) rather than staying at the high-level 'creating servers' framing.
Suggestions
Add specific concrete actions the skill covers, e.g., 'defining tools and resources, configuring transports, structuring server code, handling authentication' 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 user building MCP servers would naturally mention. | 3 / 3 |
Distinctiveness Conflict Risk | MCP server development is a very specific niche with distinct trigger terms (MCP, Model Context Protocol, FastMCP, MCP SDK). Unlikely to conflict with general coding skills or other integration-related skills. | 3 / 3 |
Total | 11 / 12 Passed |
Implementation
57%Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.
This is a well-structured MCP server development guide with excellent progressive disclosure and clear phased workflow. Its main weaknesses are the lack of inline executable code examples (deferring nearly all concrete implementation to reference files) and some verbosity in explanations that Claude wouldn't need. The workflow would benefit from explicit validation checkpoints and error recovery steps.
Suggestions
Add at least one minimal but complete inline code example (e.g., a basic TypeScript tool registration with Zod schema) so the main skill file has actionable, copy-paste ready content rather than deferring everything to reference files.
Add explicit validation feedback loops in Phase 3, e.g., 'If build fails: check type errors → fix → rebuild. Only proceed to Inspector testing when build succeeds.'
Remove the duplicated Reference Files section at the bottom, or consolidate it with the inline references in the phases to reduce token usage.
| Dimension | Reasoning | Score |
|---|---|---|
Conciseness | The skill contains some unnecessary explanation (e.g., explaining why TypeScript is recommended with multiple justifications, restating concepts like 'The quality of an MCP server is measured by how well it enables LLMs to accomplish real-world tasks'). However, it's mostly structured efficiently and avoids the worst verbosity. Some sections like the Reference Files at the end largely duplicate information already presented in the phases. | 2 / 3 |
Actionability | The skill provides a clear process and references to external guides, but the main body itself lacks executable code examples or copy-paste ready commands. Most concrete implementation details are deferred to reference files. The inline guidance is more descriptive ('Create shared utilities: API client with authentication, Error handling helpers') than instructive with specific code. | 2 / 3 |
Workflow Clarity | The four-phase workflow is clearly sequenced and logically organized. However, validation checkpoints are weak—Phase 3 mentions 'Run npm run build' and 'Test with MCP Inspector' but lacks explicit feedback loops (e.g., what to do if build fails, how to verify tools work correctly before proceeding). For a process involving server development with potential destructive operations, the missing validation/retry patterns cap this at 2. | 2 / 3 |
Progressive Disclosure | Excellent progressive disclosure with a clear overview in the main file and well-signaled one-level-deep references to language-specific guides, best practices, evaluation guide, and SDK documentation. References are clearly labeled with emoji icons and brief descriptions of what each contains. | 3 / 3 |
Total | 9 / 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.
- Repository
- anthropics/skills
- Commit
98669c1
- Reviewed
Table of Contents
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