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/onesimplecode/agent-engineering-standardsWrote 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/onesimplecode/agent-engineering-standards/agent-security)<a href="https://agentmods.dev/rules/onesimplecode/agent-engineering-standards/agent-security"><img src="https://agentmods.dev/badge/rules/onesimplecode/agent-engineering-standards/agent-security/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/onesimplecode/agent-engineering-standards/agent-security"><img src="https://agentmods.dev/badge/rules/onesimplecode/agent-engineering-standards/agent-security.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 | $0.00617 | $0.00617 |
| Opus 5.5 | $0.00247 | $0.00247 |
| Sonnet 5.5 | $0.00123 | $0.00123 |
| Haiku 4.5 | $0.00062 | $0.00062 |
Grade A, and why
agent-security 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.
How it starts
The opening of the file, as written. The whole thing — 21 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Agent Security
TR-SEC-010 — Agent tool permission grants are a security boundary (least agency)
Permission allowlists for coding agents (e.g. tool-grant or command-allowlist config) are security boundaries, not conveniences: a prompt-injected agent session (TR-SEC-005) can invoke any allowlisted command without human review. Wildcard grants for arbitrary file writes, package installation, unrestricted exec, or unrestricted network access must not be allowlisted; grant the specific command needed instead. This is OWASP's least-agency principle (least privilege extended to what an agent tool can do, how often, and where) applied to agent tooling. Review all agent permission grants at each governance review (TR-GOV-006). Counters MITRE ATT&CK T1059 (Command and Scripting Interpreter) and T1195.002 executed through trusted developer tooling.
TR-SEC-013 — Two-layer isolation for multi-agent tool and data access
When multiple agents share one backing service (a tool surface and the data behind it), isolation must be enforced at two independent layers, not one. Layer one is the tool-registry/authorization scope — distinct credentials per agent, with the server deciding which tools each credential may even invoke; this bounds what is offered to a given agent's own reasoning. Layer two is the data-layer scope — per-agent database roles or equivalent, bounding what is reachable regardless of what the authorization layer believes it has granted. Neither layer is a substitute for the other: a bug in the tool-registry layer (a stray wildcard registration, a misrouted credential map) can hand an agent a tool it should never have received, and the data-layer role is what still blocks the resulting call; a data layer alone, with no tool-registry scope, would still let a compromised or over-broad tool call reach every table a shared credential can see. Extends TR-SEC-010's least-agency principle from single-agent tool grants to multi-agent tool and data boundaries. The most-exposed agent (the one with an external input path) gets the narrowest grant at both layers; the most broadly-privileged agent gets no external egress at all.
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 · 21 lines · 617 tokens per session scan A bff8addadf2e
agent-security is a cursor rule published in the GitHub repository onesimplecode/agent-engineering-standards (3 stars, last pushed 1mo ago), licensed MIT. It adds 617 tokens to every session, about $0.0025 per session on Opus 5.5. 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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