use-existing-apis

use-existing-apis is a cursor rule for Cursor from jvaill/Kill-The-Backlog. It costs 258 tokens per session, scanned A, original, AGPL-3.0.

A coding rule that tells the agent to check whether an existing library or package already has the needed method before writing a manual implementation.

In plain words
What is it for?
It is for deciding how to implement a requested behavior when working with existing libraries or packages.
Why use it?
It reduces duplicate code and avoids reimplementing functions that the project's dependencies already provide.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/.

Good fit It is for deciding how to implement a requested behavior when working with existing libraries or packages.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/jvaill/kill-the-backlog/use-existing-apis
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.

Clone the repo
git clone --depth 1 https://github.com/jvaill/Kill-The-Backlog

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 use-existing-apis

README.md
[![agentmods](https://agentmods.dev/badge/rules/jvaill/kill-the-backlog/use-existing-apis/github.svg)](https://agentmods.dev/rules/jvaill/kill-the-backlog/use-existing-apis)
Your own site
<a href="https://agentmods.dev/rules/jvaill/kill-the-backlog/use-existing-apis"><img src="https://agentmods.dev/badge/rules/jvaill/kill-the-backlog/use-existing-apis/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.

agentmods 80×15 button for use-existing-apis

Your own site · 80×15
<a href="https://agentmods.dev/rules/jvaill/kill-the-backlog/use-existing-apis"><img src="https://agentmods.dev/badge/rules/jvaill/kill-the-backlog/use-existing-apis.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 258 This file is loaded in full into every session.
When invoked 258 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00258 $0.00258
Opus 5.5 $0.00103 $0.00103
Sonnet 5.5 $0.00052 $0.00052
Haiku 4.5 $0.00026 $0.00026

Measured 28d ago against content hash 7b70d902b020, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

use-existing-apis 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 28d 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/use-existing-apis.mdc · 26 lines

The source is not reproduced here

Licensed AGPL-3.0

The repository is licensed AGPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

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. 28d ago First seen · 26 lines · 258 tokens per session scan A 7b70d902b020

Subscribe to this mod's changes

use-existing-apis is a cursor rule published in the GitHub repository jvaill/Kill-The-Backlog (13 stars, last pushed 5mo ago), licensed AGPL-3.0. It adds 258 tokens to every session, about $0.0010 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 2026-10-02.