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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).

1.51x
Quality

74%

Does it follow best practices?

Impact

97%

1.51x

Average score across 3 eval scenarios

SecuritybySnyk

Passed

No findings from the security scan

Fix and improve this skill with Tessl

tessl review fix ./skills/anthropic-mcp-builder/SKILL.md
SKILL.md
Quality
Evals
Security

Quality

Content

63%Weight 40%Scale 1-5

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

The body is a well-organized process guide with genuinely concrete commands, URLs, and a clear four-phase workflow including validation checkpoints. Its weaknesses are avoidable duplication (SDK docs and guide links repeated between the process sections and the Reference Files section, plus generic best-practice prose), and a progressive-disclosure structure whose five referenced guide files are absent from the bundle, leaving the skill's detailed content unreachable as shipped.

Suggestions

Ship the five referenced guide files (mcp_best_practices.md, node_mcp_server_v2.md, node_mcp_server.md, python_mcp_server.md, evaluation.md) in a references/ directory and fix the './reference/' link paths so the one-level-deep disclosure structure actually resolves.

De-duplicate the SDK URLs and guide links between Phase 1.3/2.1 and the 'Reference Files' section — keep one canonical, load-timing-annotated reference list.

Trim knowledge Claude already has (e.g. the tool-naming and context-management prose in 1.1 and the rationale for recommending TypeScript) and mention the scripts/ evaluation tooling directly in Phase 4 so it is discoverable without the missing evaluation guide.

DimensionReasoningScore

Conciseness

The body is mostly tight bullets and concrete commands, but contains avoidable redundancy: SDK URLs and guide links are listed twice (in Phase 1.3/2.1 and again in the 'Reference Files' section), the Overview restates the description nearly verbatim, and sections like 'Clear, descriptive tool names help agents find the right tools quickly' explain knowledge Claude already has. This is more than the 'minor instances' of anchor 4 but not the heavily padded state of anchor 2.

3 / 5

Actionability

Provides many concrete, executable items: the spec sitemap URL with the '.md' suffix trick, exact WebFetch URLs for SDK READMEs, 'npx @modelcontextprotocol/codemod@latest v1-to-v2 .', 'npm run build', 'npx @modelcontextprotocol/inspector', 'python -m py_compile your_server.py', and a complete XML output example. It is not fully copy-paste-ready end-to-end because core implementation detail is deferred to the language guides, keeping it below anchor 5, but the commands are real and executable, above anchor 3's pseudocode level.

4 / 5

Workflow Clarity

Four phases (Research/Planning, Implementation, Review/Test, Evaluations) are clearly sequenced with validation checkpoints: 'Run npm run build to verify compilation', 'run the self-check script ... against the built server', 'Test with MCP Inspector', and Phase 4's 'Solve each question yourself to verify answers'. It falls short of anchor 5 because error-recovery feedback loops (what to do when build or tests fail) are implicit or deferred rather than explicit.

4 / 5

Progressive Disclosure

As written, the body is an overview with well-signaled, one-level-deep references and explicit load timing ('Load During Phase 1/2', 'Load During Phase 4'), and scripts/ ships real evaluation tooling. However, scoring against the actual bundle: none of the five referenced './reference/*.md' files (mcp_best_practices.md, node_mcp_server_v2.md, node_mcp_server.md, python_mcp_server.md, evaluation.md) exist in the bundle, so every detailed-content link is broken and the scripts are discoverable only through the missing evaluation guide. This falls between anchor 3 and anchor 4: the signaling and structure exceed anchor 3's muddled profile, but the non-functional reference structure is more than the 'minor organization gap' of anchor 4, so the best fit lands at 3.

3 / 5

Total

14

/

20

Passed

Description

73%Weight 40%Scale 1-5

Based on the skill's description, can an agent find and select it at the right time? Clear, specific descriptions lead to better discovery.

The description is well-constructed: it names a clear niche, uses third person, includes an explicit 'Use when...' clause with natural trigger terms, and mentions both supported language stacks. Its main limitations are modest action specificity (one core action rather than a list) and a single-scenario trigger clause rather than varied trigger phrases.

DimensionReasoningScore

Specificity

Names the domain ('creating high-quality MCP servers that enable LLMs to interact with external services through well-designed tools') with 1-2 concrete actions, but does not enumerate several distinct actions such as tool design, testing, or evaluation. It falls short of anchor 4 ('lists several specific actions') while exceeding anchor 2, which requires only generic actions.

3 / 5

Completeness

Explicitly answers both what ('Guide for creating high-quality MCP servers that enable LLMs to interact with external services through well-designed tools') and when ('Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP) or Node/TypeScript'). The 'when' clause is explicit but covers a single trigger scenario rather than the varied concrete trigger phrases of anchor 5, and the explicit 'Use when...' clause rules out the cap at 3.

4 / 5

Trigger Term Quality

Includes good natural keywords a user would say: 'building MCP servers', 'integrate external APIs or services', 'Python (FastMCP)', 'Node/TypeScript (MCP SDK)'. A few natural variations are missing (e.g. 'MCP tool', 'expose an API as tools'), so it does not reach anchor 5's comprehensive synonym coverage but clearly exceeds anchor 3's partial coverage.

4 / 5

Distinctiveness Conflict Risk

'MCP (Model Context Protocol) servers' defines a clear niche with distinct triggers and minimal conflict risk; no other common skill category would compete for these triggers. It matches anchor 5 rather than anchor 4, which requires some overlap with closely related skills.

5 / 5

Total

16

/

20

Passed

Validation

93%

Checks the skill against the spec for correct structure and formatting. All validation checks must pass before discovery and implementation can be scored.

Validation — 15 / 16 Passed

Validation for skill structure

CriteriaDescriptionResult

relative_links

Relative link issues: 14 missing

Warning

Total

15

/

16

Passed

Repository

boisenoise/skills-collections

Path

skills/anthropic-mcp-builder/SKILL.md

Reviewed

Table of Contents

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