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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).

73

1.60x
Quality

62%

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 ./claude/skills/mcp-builder/SKILL.md
SKILL.md
Quality
Evals
Security

Quality

Content

35%

Reviews the quality of instructions and guidance provided to agents. Good implementation is clear, handles edge cases, and produces reliable results.

This skill provides a comprehensive but overly verbose guide to MCP server development. Its main strength is the well-structured four-phase workflow with clear progressive disclosure to reference files. However, it suffers from significant redundancy (repeating the same file references 3-4 times), excessive explanation of concepts Claude already understands, and a lack of concrete executable code examples in the main body — deferring nearly all implementation specifics to reference files while filling the main document with abstract guidance.

Suggestions

Cut the content by 40-50%: remove the agent-centric design principles section (1.1) or reduce it to a bullet list of 5 key points, eliminate the repeated reference file links (list them once in a Reference section), and remove explanations of basic concepts like DRY, error handling, and type safety.

Add at least one concrete, executable code example in the main body — e.g., a minimal working MCP tool registration in Python or TypeScript — rather than deferring all code to reference files.

Consolidate all reference file links into a single section and remove the duplicate links scattered throughout Phases 1-4, replacing them with brief inline notes like 'see Reference Files below'.

Add explicit validation checkpoints with concrete pass/fail criteria in Phase 3.2, such as a validate-fix-retry loop with specific commands and expected outputs for both Python and TypeScript.

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 padded descriptions like 'The quality of an MCP server is measured by how well it enables LLMs to accomplish real-world tasks.' The agent-centric design principles section (1.1) is largely general software design wisdom that doesn't need spelling 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`), but most of the content is procedural description rather than executable code. The actual implementation details are deferred to reference files, and the main body contains mostly abstract instructions like 'implement proper error handling' and 'use shared utilities to avoid code duplication' without concrete examples.

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 feedback loop is vague ('verify Python syntax', 'ensure it completes without errors'). The critical warning about servers hanging is a good safety note, but there's no explicit validate-fix-retry loop for the implementation phases. The testing guidance lacks concrete validation criteria.

2 / 3

Progressive Disclosure

The skill does reference multiple external files (python_mcp_server.md, node_mcp_server.md, evaluation.md, mcp_best_practices.md) with clear links, which is good structure. However, the same references are repeated 3-4 times throughout the document (e.g., the Python guide is linked in Phase 1.4, Phase 2.1, Phase 2.4, Phase 3.3, and the Reference Files section). The Reference Files section at the bottom essentially duplicates all the links already given inline. No bundle files were provided to verify the references exist.

2 / 3

Total

7

/

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 trigger guidance with framework-specific keywords. Its main weakness is that the 'what' portion is somewhat high-level—it describes the purpose of MCP servers rather than listing the specific concrete actions the skill teaches (e.g., defining tool schemas, handling transport layers, structuring server code).

Suggestions

Add more specific concrete actions the skill covers, e.g., 'define tool schemas, implement request/response handlers, configure transport layers, structure server projects' 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 it doesn't list multiple specific concrete actions like 'define tool schemas, handle authentication, implement request routing, validate inputs'.

2 / 3

Completeness

Clearly answers both 'what' (creating MCP servers that enable LLMs to interact with external services through well-designed tools) and 'when' (explicit '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', 'external APIs', 'services', 'Python', 'FastMCP', 'Node', 'TypeScript', 'MCP SDK'. 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
einverne/dotfiles
Reviewed

Table of Contents

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