agent-development

A guide for creating and configuring coding agents, including their instructions, tools, triggers, and related settings. An agent is a software worker that follows a defined prompt to perform tasks.

In plain words
What is it for?
Use it when adding an agent, writing a subagent, defining its frontmatter, choosing its trigger description, or configuring its tools and appearance.
Why use it?
It helps avoid guessing how an agent should be described, when it should run, or which tools it may use. It also covers terms such as MCP servers, which connect agents to external tools and services.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/proxify-dev/agentic-playbook/agent-development
Any agent
npx skills add proxify-dev/agentic-playbook --skill agent-development
Clone the repo
git clone --depth 1 https://github.com/proxify-dev/agentic-playbook

Made for: Claude Code, Codex.

Per session 95 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,063 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin unknown No closer match found 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 $0.00095 $0.03063
Opus 5 $0.00048 $0.01532
Sonnet 5 $0.00019 $0.00613
Haiku 4.5 $0.00010 $0.00306

Measured yesterday against content hash e0cc7fb97199, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

agent-development 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 yesterday.

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.

skills/agent-development/SKILL.md · 483 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Files

What ships with it

6 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. yesterday First seen · 483 lines · 95 tokens per session scan A e0cc7fb97199

Subscribe to this mod's changes

agent-development is a skill published in the GitHub repository proxify-dev/agentic-playbook (2 stars, last pushed 9d ago), with no licence file. It adds 95 tokens to every session and 3,063 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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