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 necessar...

Install with Tessl CLI

npx tessl i github:sickn33/antigravity-awesome-skills --skill agent-tool-builder

What are skills?

1.05x

Quality

11%

Does it follow best practices?

Impact

100%

1.05x

Average score across 3 eval scenarios

Optimize this skill with Tessl

npx tessl skill review --optimize ./skills/agent-tool-builder/SKILL.md

SKILL.md

Review

Evals

Discovery

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 description is severely truncated and provides no actionable information about what the skill does or when to use it. The visible content is abstract philosophical commentary about tool design rather than a functional skill description. It fails on all dimensions due to incompleteness and lack of specificity.

Suggestions

Complete the description - it appears to be cut off mid-sentence. Ensure the full text is included in the YAML frontmatter.

Add specific concrete actions the skill performs (e.g., 'Designs tool schemas, validates API contracts, generates tool documentation').

Include an explicit 'Use when...' clause with natural trigger terms users would say (e.g., 'Use when building MCP tools, designing agent interfaces, or creating function schemas').

Dimension	Reasoning	Score
Specificity	The description is truncated and only contains abstract language about 'tools' and 'AI agents' without listing any concrete actions the skill performs.	1 / 3
Completeness	The description is cut off mid-sentence and fails to answer either 'what does this do' or 'when should Claude use it'. There is no 'Use when...' clause or equivalent guidance.	1 / 3
Trigger Term Quality	The visible portion contains technical jargon ('AI agents', 'hallucinates', 'tokens') but no natural keywords a user would say when needing this skill. No actionable trigger terms are present.	1 / 3
Distinctiveness Conflict Risk	The generic reference to 'tools' and 'AI agents' is extremely broad and would conflict with virtually any agent-related or tool-building skill.	1 / 3
	Total	4 / 12 Passed

Implementation

22%

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

This skill is essentially a skeleton with headers but no substantive content. It identifies important concepts (schema design, error handling, input examples) but fails to provide any actionable guidance, code examples, or concrete instructions. The anti-patterns are listed without explanation, making them useless for teaching Claude what to avoid.

Suggestions

Add executable code examples for each pattern (e.g., a complete JSON Schema example for 'Tool Schema Design' showing good vs bad descriptions)

Fill in the anti-pattern sections with concrete examples of what NOT to do and why they fail

Include a step-by-step workflow for designing a tool: 1) Define purpose, 2) Write description first, 3) Design schema, 4) Add examples, 5) Test with sample prompts

Add actual tool schema examples showing input validation, error response formats, and description best practices

Dimension	Reasoning	Score
Conciseness	The content is relatively brief but includes some unnecessary philosophical framing ('Your core insight...') that Claude already understands. The capabilities list and pattern headers without content add tokens without value.	2 / 3
Actionability	The skill provides no concrete code, commands, or executable examples. Pattern sections are empty headers with no actual guidance. Anti-patterns are listed but not explained or demonstrated.	1 / 3
Workflow Clarity	There is no workflow, sequence, or process defined. The content describes what good tools are conceptually but provides no steps for actually building them or validating the output.	1 / 3
Progressive Disclosure	The structure with sections (Patterns, Anti-Patterns, Related Skills) shows organizational intent, but the sections are empty shells. No references to detailed documentation or examples are provided.	2 / 3
	Total	6 / 12 Passed

Validation

90%

Warnings & errors only

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

Validation — 10 / 11 Passed

Validation for skill structure

Criteria	Description	Result
frontmatter_unknown_keys	Unknown frontmatter key(s) found; consider removing or moving to metadata	Warning

	Total	10 / 11 Passed

Reviewed: about 5 hours ago

Table of Contents

Discovery Implementation Validation

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