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.
git clone --depth 1 https://github.com/vibeeval/vibecosystemWrote 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/rules/vibeeval/vibecosystem/agent-development)<a href="https://agentmods.dev/rules/vibeeval/vibecosystem/agent-development"><img src="https://agentmods.dev/badge/rules/vibeeval/vibecosystem/agent-development/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.
<a href="https://agentmods.dev/rules/vibeeval/vibecosystem/agent-development"><img src="https://agentmods.dev/badge/rules/vibeeval/vibecosystem/agent-development.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00000 | $0.00293 |
| Opus 5.5 | $0.00000 | $0.00117 |
| Sonnet 5.5 | $0.00000 | $0.00059 |
| Haiku 4.5 | $0.00000 | $0.00029 |
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 1mo 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.
What it actually says
Agent Development Rules
Agent File Format
Each agent is a Markdown file with YAML frontmatter:
---
name: agent-name
description: One-line description of what the agent does
tools: [Read, Write, Edit, Bash, Grep, Glob]
---
Followed by the agent's system prompt in Markdown.
Naming Conventions
- Filename:
kebab-case.md(e.g.,code-reviewer.md) - Name field: same as filename without extension
- Description: starts with a verb (e.g., "Reviews code for...")
Agent Categories
- Core Dev: frontend-dev, backend-dev, kraken, spark, devops
- Review & QA: code-reviewer, security-reviewer, verifier, qa-engineer
- Domain Experts: graphql-expert, kubernetes-expert, ddd-expert
- Architecture: architect, planner, clean-arch-expert
- Testing: tdd-guide, e2e-runner, arbiter, mocksmith
- Analysis: scout, sleuth, data-analyst, profiler
Quality Rules
- Every agent must have a clear, specific purpose
- Avoid overlapping responsibilities between agents
- Keep system prompts focused and actionable
- Include specific output format expectations
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.
- 1mo ago First seen · 41 lines · 0 tokens per session scan A bf72891afd96
agent-development is a cursor rule published in the GitHub repository vibeeval/vibecosystem (536 stars, last pushed 2mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 293 tokens. 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 2026-08-30.
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