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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).

76

1.60x
Quality

66%

Does it follow best practices?

Impact

88%

1.60x

Average score across 3 eval scenarios

SecuritybySnyk

Advisory

Suggest reviewing before use

Optimize this skill with Tessl

npx tessl skill review --optimize ./skills/data/0b1c2d3e-4f5a-6b7c-8d9e-0f1a2b3c4d5e/SKILL.md
SKILL.md
Quality
Evals
Security

Quality

Content

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 strong organizational structure and progressive disclosure but suffers from significant verbosity and limited actionability in the main body. It reads more like a project management guide than a technical skill, with most concrete implementation details deferred to reference files. The workflow is logical but lacks explicit validation gates and feedback loops that would make it more robust.

Suggestions

Cut the content by 40-50%: remove explanations of obvious concepts (what DRY means, what error handling is, what MCP is), eliminate redundant references to the same guide files, and tighten phrasing throughout.

Add at least one complete, minimal working example of an MCP server (either Python or TypeScript) directly in the main skill body so Claude has an executable template without needing to load reference files.

Add explicit validation gates with pass/fail criteria at phase transitions, e.g., 'Do not proceed to Phase 2 until: plan includes at least 5 tools, input/output schemas are defined, error strategy is documented.'

Consolidate the repeated reference file listings—the same files are referenced in Phase 1, Phase 2, Phase 3, and the Reference Files section. List them once with clear 'load when needed' annotations.

DimensionReasoningScore

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, while useful, is padded with explanations of obvious concepts.

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`), but most of the content is high-level direction rather than executable code. The actual implementation details are deferred to reference files. There's no complete working code example in the main skill body—just instructions to load other files that presumably contain examples.

2 / 3

Workflow Clarity

The four-phase workflow is clearly sequenced and logically organized, but validation checkpoints are weak. Phase 3 mentions testing but the validation steps are vague ('review the code for...') rather than explicit pass/fail gates. The warning about servers hanging is a good safety note, but there's no explicit feedback loop for 'if build fails, do X; if evaluation scores are low, revisit Y'. The quality checklist is deferred entirely to reference files.

2 / 3

Progressive Disclosure

The skill effectively uses progressive disclosure with a clear overview in the main file and well-signaled one-level-deep references to language-specific guides, best practices, and evaluation guides. References are clearly labeled with emoji icons and descriptive summaries of what each file contains. The 'Reference Files' section at the end provides a clean navigation index. However, without bundle files to verify, we evaluate the structure as presented, which is well-organized.

3 / 3

Total

8

/

12

Passed

Description

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 the 'what' portion is somewhat high-level—it could benefit from listing more specific concrete actions like defining tools, configuring transports, or handling authentication. Overall it performs well for skill selection purposes.

Suggestions

Add more specific concrete actions to the 'what' portion, e.g., 'defining tools and resources, configuring transports, handling authentication, and structuring server code' to improve specificity.

DimensionReasoningScore

Specificity

The description 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 does not 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) and 'when' ('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', and '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). This is unlikely to conflict with general coding skills or other integration-related skills.

3 / 3

Total

11

/

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.

Validation11 / 11 Passed

Validation for skill structure

No warnings or errors.

Repository
majiayu000/claude-skill-registry
Reviewed

Table of Contents

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