behavioral_rules

A set of development rules for working in an existing software project. It covers project inspection, checking external documentation, cautious edits, tool use, and clear communication during implementation.

In plain words
What is it for?
Use it to guide coding tasks that require examining the existing structure, verifying library or API details, choosing simple changes, checking affected code, and explaining decisions and results.
Why use it?
It helps prevent unnecessary project rewrites, outdated technical decisions, accidental deletions, and changes made without understanding their impact. It also sets expectations for verification and persistence when tasks are incomplete.

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/lastbotinc/cursor-rules-tools/behavioral_rules
Clone the repo
git clone --depth 1 https://github.com/LastBotInc/cursor-rules-tools

Made for: Cursor.

Per session 467 This file is loaded in full into every session.
When invoked 467 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin original 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 $0.00467 $0.00467
Opus 5 $0.00234 $0.00234
Sonnet 5 $0.00093 $0.00093
Haiku 4.5 $0.00047 $0.00047

Measured yesterday against content hash ce6d85f3e79b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

behavioral_rules 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 yesterday.

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/behavioral_rules.mdc · 34 lines

What it actually says

<behavioral_rules>

  • Existing Project: NEVER create a new project. Analyze existing structure.
  • Up-to-date Info: Do NOT rely solely on internal knowledge. ALWAYS use web_search or gemini --ground to verify external API/library documentation, versions, and best practices.
  • Latest Libraries: Prefer latest stable versions for dependencies.
  • Cautious Edits: Use codebase_search/grep_search to understand impact before modifying existing code. Avoid deletions unless clearly required.
  • Follow Instructions: Adhere precisely to <workflow> steps and these rules.
  • Persistence: Be persistent, do not give up. Don't stop when you have not completed the task.
  • Simplicity: Prefer the simplest, most direct solution meeting all requirements.
  • Tool Usage: Use provided tools appropriately. Explain why a tool is used and how the prompt is constructed (especially for Gemini).
  • Clarity: Communicate plans, workflows, results clearly. Ask clarifying questions if ambiguous.

Model-Specific Behavior:

  • For Claude (Anthropic):

    • Exact Request Fulfillment: Implement only what is explicitly asked. No extras.
    • Confirm all parts of the request are addressed, nothing more.
    • Ask: "Am I adding anything not explicitly requested?" If yes, remove it.
    • Avoid suggesting alternatives unless asked.
  • For Gemini (Google):

    • Follow Instructions Precisely: Execute user instructions exactly as written.
    • Adhere Strictly: Follow the specified workflow and steps rigorously.
    • Maintain Structure: Use consistent formatting as specified.
    • Leverage Context: Actively incorporate context from documentation (*.md), rules (*.mdc), codebase searches (codebase_search), and files/URLs into prompts.
    • Iterate When Necessary: Refine outputs through follow-up prompts if needed.
  • For GPT (OpenAI) and Grok (X.AI):

    • Be complete, aim for full task completion per run.
    • Only ask user for major decisions. </behavioral_rules>
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. yesterday First seen · 34 lines · 467 tokens per session scan A ce6d85f3e79b

Subscribe to this mod's changes

behavioral_rules is a cursor rule published in the GitHub repository LastBotInc/cursor-rules-tools (3 stars, last pushed 1y ago), licensed MIT. It adds 467 tokens to every session, about $0.0023 per session on Opus 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.