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.
npx agentmods add skills/chankov/agent-fleet/designing-agentsnpx skills add chankov/agent-fleet --skill designing-agentsgit clone --depth 1 https://github.com/chankov/agent-fleetWrote 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.
[](https://agentmods.dev/skills/chankov/agent-fleet/designing-agents)<a href="https://agentmods.dev/skills/chankov/agent-fleet/designing-agents"><img src="https://agentmods.dev/badge/skills/chankov/agent-fleet/designing-agents.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00082 | $0.05503 |
| Opus 5 | $0.00041 | $0.02752 |
| Sonnet 5 | $0.00016 | $0.01101 |
| Haiku 4.5 | $0.00008 | $0.00550 |
Grade A, and why
designing-agents 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 5d ago.
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.
How it starts
The opening of the file, as written. The whole thing — 395 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Designing Agents
Overview
This repo has three kinds of artifacts that shape how an agent works. Each is authored, versioned, and invoked deliberately:
- Agent personas live in
agents/<name>.md. They define a role another agent adopts when it needs specialized review, audit, or analysis. Example:code-reviewer,security-auditor,test-engineer. - Skills live in
skills/<name>/SKILL.md. They define a workflow — a repeatable process with gated steps, anti-rationalization guardrails, and verification. Example:spec-driven-development,test-driven-development,context-engineering. - pi harnesses live in
.pi/harnesses/<name>/. They define a session environment — a TypeScript pi extension that reshapes the whole session: setting UI surfaces, gating tool calls, registering new tools or commands, or orchestrating sub-agents. Example:agent-hub,damage-control,coms.
Personas and skills are prose that change an agent's judgment. A harness is code that changes the agent's environment — what it can do and what it sees. All three fail the same way: a persona that reads like general advice gets cited but ignored; a skill that skips its guardrails becomes a suggestion; a harness built without studying the existing ones collides with pi's auto-discovery or fights another extension. This skill is the workflow for authoring any of the three so the result measurably changes behavior.
When to Use
- Creating a new persona file in
agents/(reviewer, auditor, domain specialist) - Creating a new skill directory in
skills/(a process, checklist, or workflow) - Creating a new pi harness in
.pi/harnesses/(a footer, focus gate, safety check, orchestrator, or messaging layer) - An existing persona, skill, or harness is vague, overlaps another, or is being ignored in practice
- A recurring review, workflow, or session-shaping need has emerged and deserves its own artifact
- Rewriting an older artifact to align with current writing standards
What ships with it
1 file 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.
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.
- 5d ago First seen · 395 lines · 82 tokens per session scan A 2e75d3499f41
designing-agents is a skill published in the GitHub repository chankov/agent-fleet (13 stars, last pushed yesterday), licensed MIT. It adds 82 tokens to every session and 5,503 once invoked, about $0.0004 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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