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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

Quality

49%

Does it follow best practices?

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SecuritybySnyk

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

The canonical home for this skill is agent-tool-builder in sickn33/agentic-awesome-skills

SKILL.md
Quality
Evals
Security

Quality

Content

22%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 skeleton: a padded, truncated persona intro followed by one-line pattern glosses and completely empty anti-pattern sections. It contains no actionable guidance — no schema example, no good-vs-bad description comparison, no error-response format — so an agent invoking this skill would learn the thesis (descriptions matter more than implementations) but not what to do.

Suggestions

Add concrete, executable content: a good vs. bad tool description pair, a minimal JSON Schema example with well-chosen descriptions, and a recoverable error-response format — these directly address the actionability score of 1.

Define a workflow for when the skill is invoked (e.g. 1. Review the tool's schema, 2. Rewrite descriptions using the pattern, 3. Define error responses, 4. Validate the schema) so Claude has a sequence to follow instead of only a persona.

Fill in or remove the empty Anti-Pattern sections, each with a one-line example of the failure and its fix, and trim the truncated persona intro to a single sentence.

DimensionReasoningScore

Conciseness

The body is short and mostly terse, but the opening persona paragraph ('You are an expert in the interface between LLMs and the outside world... A simple tool with crystal-clear documentation will succeed') is motivational padding that adds no guidance, and it too is truncated ('You push for explicit error hand'). It does not fall to score 2 because only one section is padded and no space is spent explaining concepts Claude already knows.

3 / 5

Actionability

There is no code, command, or example anywhere in the body — even the highest-value content, the pattern and anti-pattern sections, is purely nominal ('Returning errors that help the LLM recover', '❌ Vague Descriptions'). This matches the score 1 anchor: it only describes rather than instructs.

1 / 5

Workflow Clarity

No steps or sequence of any kind are present; the body never tells Claude what to actually do when the skill is invoked (no design procedure, no review checklist, no validation of schemas). This matches the score 1 anchor of steps missing with no sequence; score 2 would require at least a rough sequence, which is absent.

1 / 5

Progressive Disclosure

The body is short with clear section headers (Capabilities, Patterns, Anti-Patterns, Related Skills) and no nested references, but the three Anti-Pattern headers ('❌ Vague Descriptions', '❌ Silent Failures', '❌ Too Many Tools') are completely empty, and no bundle files exist to carry the example material this topic needs. It does not reach score 4 because empty sections and missing example content leave the organization incomplete rather than just minor-gapped.

3 / 5

Total

8

/

20

Passed

Description

53%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 communicates a clear domain and several specific topics, but it reads more like a marketing blurb than a trigger: two sentences of motivational framing, no 'Use when...' guidance, and text truncated mid-word. It would reliably inform a reader what the skill is about but gives little help in deciding when to invoke it.

Suggestions

Replace the motivational framing ('A well-designed tool is the difference between...') with a concrete action list, e.g. 'Design tool JSON schemas, write tool descriptions, and structure tool error responses for LLM agents, including MCP tools.'

Append an explicit trigger clause, e.g. 'Use when building or reviewing tools, function calling, MCP servers, or tool schemas for AI agents.'

Fix the truncated text — the description ends mid-word ('implementa') — and add missing natural trigger terms such as 'function calling' and 'tool use'.

DimensionReasoningScore

Specificity

The description enumerates specific topics ('JSON Schema best practices, description writing that actually helps the LLM, validation, and the emerging MCP standard') but frames them as subject areas rather than concrete actions, and pads them with motivational fluff ('A well-designed tool is the difference between an agent that works and one that hallucinates, fails silently, or costs 10x more tokens'). It is not score 4 because the listed items are topics, not executable actions, and the text is cut off mid-word ('more important than tool implementa').

3 / 5

Completeness

It answers 'what' clearly ('This skill covers tool design from schema to error handling') but contains no 'Use when...' clause or equivalent trigger guidance, capping completeness at 3 per the rubric guideline. It is not score 2 because the 'what' is concrete and multi-part, not vague.

3 / 5

Trigger Term Quality

Relevant keywords like 'tool design', 'JSON Schema', 'error handling', 'validation', and 'MCP' are present, but common natural variations users would say — 'function calling', 'tool use', 'build agent tools' — are missing. It does not reach score 4 because the keyword set lacks the synonyms and variation coverage of the higher anchor.

3 / 5

Distinctiveness Conflict Risk

The niche of AI-agent tool design with MCP and JSON Schema specifics ('Tool descriptions are more important than tool implementa...') is mostly distinct, with only minor overlap risk against closely related skills like api-designer or backend. It is not score 5 because without any 'when to use' phrasing, disambiguation from those overlapping skills relies entirely on domain keywords.

4 / 5

Total

13

/

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

metadata_version

'metadata.version' is missing

Warning

Total

15

/

16

Passed

Repository

davila7/claude-code-templates

Path

cli-tool/components/skills/ai-research/agent-tool-builder/SKILL.md

Reviewed

Table of Contents

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