xmtp

xmtp is a cursor rule for Cursor from tantodefi/xmtpauth. It costs 6,601 tokens per session, scanned A, original, MIT.

A set of rules for building XMTP agents, programs that communicate through the XMTP messaging network, with TypeScript and Node.js.

In plain words
What is it for?
Use it when creating or updating XMTP agents, including their client setup, group conversations and related TypeScript code.
Why use it?
It keeps the code aligned with the current XMTP package and recommended TypeScript module and client setup, avoiding deprecated imports and inconsistent patterns.

Cursor rule for Cursor

Written for Cursor: installed under .cursor/.

Good fit Use it when creating or updating XMTP agents, including their client setup, group conversations and related TypeScript code.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/tantodefi/xmtpauth/xmtp
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/tantodefi/xmtpauth

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 xmtp

README.md
[![agentmods](https://agentmods.dev/badge/rules/tantodefi/xmtpauth/xmtp/github.svg)](https://agentmods.dev/rules/tantodefi/xmtpauth/xmtp)
Your own site
<a href="https://agentmods.dev/rules/tantodefi/xmtpauth/xmtp"><img src="https://agentmods.dev/badge/rules/tantodefi/xmtpauth/xmtp/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 xmtp

Your own site · 80×15
<a href="https://agentmods.dev/rules/tantodefi/xmtpauth/xmtp"><img src="https://agentmods.dev/badge/rules/tantodefi/xmtpauth/xmtp.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 6,601 This file is loaded in full into every session.
When invoked 6,601 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 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 5.1 $0.06601 $0.06601
Opus 5.5 $0.02640 $0.02640
Sonnet 5.5 $0.01320 $0.01320
Haiku 4.5 $0.00660 $0.00660

Measured 2mo ago against content hash a5cc8be9b3f0, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

xmtp 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 2mo 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/xmtp.mdc · 943 lines

How it starts

The opening of the file, as written. The whole thing — 943 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Writing XMTP Agents

You're an expert in writing TypeScript with Node.js. Generate high-quality XMTP Agents that adhere to the following best practices:

Guidelines

  1. Use modern TypeScript patterns and ESM modules. All examples should be structured as ES modules with import statements rather than CommonJS require().

  2. Use the XMTP node-sdk version "2.0.2" or newer, which offers enhanced functionality including group conversations.

  3. Only import from @xmtp/node-sdk for XMTP functionality. Do not import from any other XMTP-related packages or URLs. Specifically:

    • Never use the deprecated @xmtp/xmtp-js library, which has been completely replaced by @xmtp/node-sdk
    • Always import directly from @xmtp/node-sdk as shown below:
    // CORRECT:
    import { Client, type Conversation, type XmtpEnv } from "@xmtp/node-sdk";
    
    // INCORRECT - DEPRECATED:
    import { Client } from "@xmtp/xmtp-js";
    import { XmtpClient } from "some-other-package";
    
  4. Follow the consistent pattern for initializing XMTP clients:

    const signer = createSigner(WALLET_KEY);
    const encryptionKey = getEncryptionKeyFromHex(ENCRYPTION_KEY);
    const client = await Client.create(signer, {
      dbEncryptionKey: encryptionKey,
      env: XMTP_ENV as XmtpEnv,
    });
    
  5. Use proper environment variable validation at the start of each application. Check for required environment variables and show descriptive errors if missing.

  6. Never use the concept of "topic" when working with XMTP. The current SDK doesn't use topics for message organization - work directly with conversations, groups, and DMs instead.

  7. Handle both Group and DM conversations properly. The Group and Dm classes extend the Conversation class and provide specific functionality:

    if (conversation instanceof Group) {
      // Group-specific functionality like group.name or group.addMembers
    } else if (conversation instanceof Dm) {
      // DM-specific functionality like conversation.peerInboxId
    }
    

Read the full file on GitHub · 943 lines

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. 2mo ago First seen · 943 lines · 6,601 tokens per session scan A a5cc8be9b3f0

Subscribe to this mod's changes

xmtp is a cursor rule published in the GitHub repository tantodefi/xmtpauth (3 stars, last pushed 1y ago), licensed MIT. It adds 6,601 tokens to every session, about $0.0264 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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