1c-ssl-skills: Skill for Claude Code

.agents/skills/tool-design/SKILL.md

tool-design is a skill for Claude Code, Codex from brake71/1c-ssl-skills. It costs 109 tokens per session (3,850 once invoked), scanned A, a copy of tool-design, MIT.

A guide to designing the interfaces that connect AI agents to tools. It covers tool descriptions, input and output formats, naming, error messages, and MCP servers, which let agents call external tools.

In plain words
What is it for?
Use it to define tool schemas, improve tool selection, design response formats, consolidate overlapping tools, and write errors that guide retries.
Why use it?
Unclear tool instructions can make an agent choose the wrong tool or send invalid inputs. Clear contracts and recovery messages make tool use easier to interpret and correct.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions subagents; installed under .agents/ (shared by several agents).

This is brake71/1c-ssl-skills's own configuration. It tells Claude Code and Codex how to work on 1c-ssl-skills itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything 1c-ssl-skills configures →

Reuse

Borrowing it

Nothing to install: this file belongs to brake71/1c-ssl-skills. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/brake71/1c-ssl-skills/main/.agents/skills/tool-design/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/brake71/1c-ssl-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for tool-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/brake71/1c-ssl-skills/tool-design/github.svg)](https://agentmods.dev/skills/brake71/1c-ssl-skills/tool-design)
Your own site
<a href="https://agentmods.dev/skills/brake71/1c-ssl-skills/tool-design"><img src="https://agentmods.dev/badge/skills/brake71/1c-ssl-skills/tool-design/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for tool-design

Your own site · 80×15
<a href="https://agentmods.dev/skills/brake71/1c-ssl-skills/tool-design"><img src="https://agentmods.dev/badge/skills/brake71/1c-ssl-skills/tool-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 109 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,850 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00109 $0.03850
Opus 5.5 $0.00044 $0.01540
Sonnet 5.5 $0.00022 $0.00770
Haiku 4.5 $0.00011 $0.00385

Measured 17d ago against content hash 14f5a12b6911, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

tool-design scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 17d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/description_generator.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to tool-design — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.agents/skills/tool-design/SKILL.md · 297 lines

How it starts

The opening of the file, as written. The whole thing — 297 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Tool Design for Agents

Design every tool as a contract between a deterministic system and a non-deterministic agent. Unlike human-facing APIs, agent-facing tools must make the contract unambiguous through the description alone: agents infer intent from descriptions and generate calls that must match expected formats. Every ambiguity becomes a potential failure mode that no amount of prompt engineering can fix.

The unit of work for this skill is a single tool or a tool catalog. Project-shape, pipeline architecture, task-model-fit, and cost-at-the-project-level decisions belong to project-development. Deciding whether to introduce sub-agents belongs to multi-agent-patterns. This skill owns the interface layer that connects deterministic code to the agent.

When to Activate

Activate this skill when the unit of work is a tool:

  • Writing a new tool description, schema, or response format.
  • Debugging cases where the agent picked the wrong tool or generated malformed calls.
  • Consolidating an overlapping tool catalog (the classic "we have 17 tools, the agent picks wrong half the time" case).
  • Designing actionable error messages so the agent can self-correct.
  • Naming tools and parameters consistently across a catalog (MCP namespacing, verb-noun naming).
  • Evaluating a third-party tool against the consolidation principle before adding it.

Do not activate this skill for adjacent work owned by other skills:

  • Deciding whether the project should use LLMs at all, or what the pipeline stages should be: project-development.
  • Deciding whether to split work across sub-agents or run a single agent with more tools: multi-agent-patterns.
  • Reducing the token weight of tool outputs at the trajectory level (observation masking, format-option choice at scale): context-optimization.

Core Concepts

Design tools around the consolidation principle: if a human engineer cannot definitively say which tool should be used in a given situation, an agent cannot be expected to do better. Reduce the tool set until each tool has one unambiguous purpose, because agents select tools by comparing descriptions and any overlap introduces selection errors.

Read the full file on GitHub · 297 lines

Files

What ships with it

3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 17d ago First seen · 297 lines · 109 tokens per session scan A 14f5a12b6911

Subscribe to this mod's changes

tool-design is a skill published in the GitHub repository brake71/1c-ssl-skills (82 stars, last pushed 15d ago), licensed MIT. It adds 109 tokens to every session and 3,850 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to tool-design, differing in 0 lines, and is treated as a copy.