mcp-tool-usage

mcp-tool-usage is a cursor rule for Cursor from xenitV1/cursor-dynamic-rules-system. It costs 0 tokens per session (3,004 once invoked), scanned A, original, no licence file.

A rule for using MCP tools selectively. MCP tools are connected services or utilities an agent can call; this rule reserves them for complex multi-step tasks and unfamiliar technologies.

In plain words
What is it for?
Deciding when an agent should call connected tools during a coding task.
Why use it?
It avoids using external tools for tasks that do not need them while allowing them when the work is complex or unfamiliar.

Cursor rule for Cursor

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/xenitv1/cursor-dynamic-rules-system/mcp-tool-usage
Clone the repo
git clone --depth 1 https://github.com/xenitV1/cursor-dynamic-rules-system

Made for: Cursor.

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 mcp-tool-usage

README.md
[![agentmods](https://agentmods.dev/badge/rules/xenitv1/cursor-dynamic-rules-system/mcp-tool-usage.svg)](https://agentmods.dev/rules/xenitv1/cursor-dynamic-rules-system/mcp-tool-usage)
Your own site
<a href="https://agentmods.dev/rules/xenitv1/cursor-dynamic-rules-system/mcp-tool-usage"><img src="https://agentmods.dev/badge/rules/xenitv1/cursor-dynamic-rules-system/mcp-tool-usage.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 3,004 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 $0.00000 $0.03004
Opus 5 $0.00000 $0.01502
Sonnet 5 $0.00000 $0.00601
Haiku 4.5 $0.00000 $0.00300

Measured 4d ago against content hash 42726802142e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mcp-tool-usage 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 4d 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.

.cursor/rules/protocols/mcp-tool-usage.mdc · 436 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. 4d ago First seen · 436 lines · 0 tokens per session scan A 42726802142e

Subscribe to this mod's changes

mcp-tool-usage is a cursor rule published in the GitHub repository xenitV1/cursor-dynamic-rules-system (94 stars, last pushed 10mo ago), with no licence file. It costs nothing until one of its globs matches a file; then it loads 3,004 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.