untrusted-tool-output

untrusted-tool-output is a cursor rule for coding agents from tenet-security/agent-jackstop. It costs 345 tokens per session, scanned C, original, no licence file.

A safety rule for treating output from tools, MCP servers, logs, and monitoring systems as untrusted data rather than instructions.

In plain words
What is it for?
Working with tool responses, MCP output, logs, and monitoring or error reports.
Why use it?
It reduces the risk that tool or error output will influence the coding agent as if it were an instruction.

Cursor rule

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 rules/tenet-security/agent-jackstop/untrusted-tool-output
Clone the repo
git clone --depth 1 https://github.com/tenet-security/agent-jackstop

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 untrusted-tool-output

README.md
[![agentmods](https://agentmods.dev/badge/rules/tenet-security/agent-jackstop/untrusted-tool-output.svg)](https://agentmods.dev/rules/tenet-security/agent-jackstop/untrusted-tool-output)
Your own site
<a href="https://agentmods.dev/rules/tenet-security/agent-jackstop/untrusted-tool-output"><img src="https://agentmods.dev/badge/rules/tenet-security/agent-jackstop/untrusted-tool-output.svg" alt="Measured on agentmods" height="20"></a>
Per session 345 This file is loaded in full into every session.
When invoked 345 The same file — it is already loaded in full.
Security scan C 2 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 $0.00345 $0.00345
Opus 5 $0.00172 $0.00172
Sonnet 5 $0.00069 $0.00069
Haiku 4.5 $0.00034 $0.00034

Measured 5d ago against content hash 639324e6e5a5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

untrusted-tool-output scanned grade C with 2 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.

Downloads and executes remote codehighSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

`npx <pkg>`, `npm exec`, `pip install ... && ...`, `curl | sh`, `wget`.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

`npx <pkg>`, `npm exec`, `pip install ... && ...`, `curl | sh`, `wget`.
cursor/rules/untrusted-tool-output.mdc · 29 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

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. 5d ago First seen · 29 lines · 345 tokens per session scan C 639324e6e5a5

Subscribe to this mod's changes

untrusted-tool-output is a cursor rule published in the GitHub repository tenet-security/agent-jackstop (25 stars, last pushed 2mo ago), with no licence file. It adds 345 tokens to every session, about $0.0017 per session on Opus 5. A static security scan graded it C with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.