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agent-tool-builder

Tools are how AI agents interact with the world. A well-designed tool is the difference between an agent that works and one that hallucinates, fails silently, or costs 10x more tokens than necessary. This skill covers tool design from schema to error handling. JSON Schema best practices, description writing that actually helps the LLM, validation, and the emerging MCP standard that's becoming the lingua franca for AI tools. Key insight: Tool descriptions are more important than tool implementa

66

0.99x
Quality

49%

Does it follow best practices?

Impact

99%

0.99x

Average score across 3 eval scenarios

SecuritybySnyk

Passed

No findings from the security scan

Fix and improve this skill with Tessl

tessl review fix ./cli-tool/components/skills/ai-research/agent-tool-builder/SKILL.md
SKILL.md
Quality
Evals
Security

Quality

Content

40%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 lean and sectioned but largely vacuous — it states themes about tool design without any executable schema examples, concrete patterns, or a build/validate workflow, so it offers little actionable guidance.

Suggestions

Add a concrete JSON Schema example and a tool-description example under 'Tool Schema Design' and 'Tool with Input Examples' so the guidance is executable.

Replace the persona narrative with a brief numbered workflow (define schema → write description → add validation → design error responses) with a validation checkpoint.

Fill the empty Anti-Patterns sections with a concrete bad-vs-good example for each (vague description, silent failure, tool sprawl).

DimensionReasoningScore

Conciseness

The body is short, but the persona/insight narrative ('You've seen tools that work beautifully...', 'The LLM never sees your code') is unnecessary explanation Claude doesn't need, so it is mostly efficient with some padding to trim.

3 / 5

Actionability

Only high-level hints are given ('Creating clear, unambiguous JSON Schema for tools', 'Using examples to guide LLM tool usage') with no concrete code, schema examples, or commands, and the Anti-Patterns sections are empty.

2 / 5

Workflow Clarity

Tool design is inherently multi-step (schema, examples, validation, error handling) yet no sequence is provided; only an unlinked list of patterns with many gaps and no validation checkpoints.

2 / 5

Progressive Disclosure

For a sub-50-line skill with no bundle files, the content is organized into clear sections (Capabilities, Patterns, Anti-Patterns, Related Skills); the empty Anti-Patterns headers are a minor organization gap keeping it below 5.

4 / 5

Total

11

/

20

Passed

Description

58%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 specific about what the skill covers and occupies a reasonably distinct niche, but it never tells Claude when to activate, which caps its completeness and weakens trigger quality.

Suggestions

Append an explicit trigger clause, e.g. 'Use when designing or building tools/functions for AI agents, writing JSON Schemas for tool definitions, or implementing MCP tools.'

Add natural trigger synonyms and file extensions users might say ('function calling', 'tool schema', '.mcp', 'tool definition').

Trim the opening philosophical sentence ('Tools are how AI agents interact with the world...') to keep the description concise and trigger-focused.

DimensionReasoningScore

Specificity

Names the domain and several concrete topics — 'JSON Schema best practices', 'description writing', 'validation', 'the emerging MCP standard', 'error handling' — giving multiple specific actions, though coverage of the full tool-design lifecycle has minor gaps.

4 / 5

Completeness

It clearly answers 'what' (covers tool design from schema to error handling) but offers no 'when should Claude use it' clause; per the rubric a missing 'Use when...' caps completeness at 3.

3 / 5

Trigger Term Quality

Includes relevant keywords like 'tool design', 'JSON Schema', 'MCP', and 'validation' that a user might say, but misses common variations/synonyms and lacks explicit 'Use when...' trigger phrasing.

3 / 5

Distinctiveness Conflict Risk

The agent-tool/MCP/JSON-Schema niche is mostly distinct with only minor overlap risk against closely related skills like api-designer or backend.

4 / 5

Total

14

/

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

frontmatter_unknown_keys

Unknown frontmatter key(s) found; consider removing or moving to metadata

Warning

Total

15

/

16

Passed

Repository
davila7/claude-code-templates
Reviewed

Table of Contents

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