create-mcp-server

A set of instructions for creating a Model Context Protocol (MCP) server in JavaScript. An MCP server lets an AI application access external tools, data, or prompts through a standard interface.

In plain words
What is it for?
Creating an MCP server with Node, Bun, or Deno that communicates through standard input and output or WebSockets, and supports protocol features such as tools, resources, prompts, errors, and notifications.
Why use it?
It gives the coding agent the protocol details and server setup options needed to build a compatible server instead of guessing how the SDK works.

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/zackiles/deno-kit/create-mcp-server
Clone the repo
git clone --depth 1 https://github.com/zackiles/deno-kit

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 1,368 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.01368
Opus 5 $0.00000 $0.00684
Sonnet 5 $0.00000 $0.00274
Haiku 4.5 $0.00000 $0.00137

Measured yesterday against content hash 58c4e5145446, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

create-mcp-server 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.

Origin

This is a copy

100% identical to create-mcp-server — 202 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.cursor/rules/create-mcp-server.mdc · 105 lines

How it starts

The opening of the file, as written. The whole thing — 105 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Context

@modelcontextprotocol/sdk is an SDK for the Model Context Protocol. The full specifcation of the protocol can be found at https://raw.githubusercontent.com/modelcontextprotocol/specification/refs/heads/main/schema/draft/schema.json

Task

You'll write an MCP server given the available backend Javascript runtime available to you (e.g. Deno, Bun, Node) that supports invoking the server as either a stdio or WebSocket server using the native capabilities of the Javascript runtime available to you. using the native stdio and/or WebSocket available.

Mandatory Reading Before Starting

Understand the depdency @modelcontextprotocol/sdk by reading its README. Understand it's method, types and interfaces, and the two was in which it allows starting a server (the high level, and the lower level for finer control and configuration). Understand the various helper methods it provides. Understand its core components: Resources, Prompts, Tools, Notifications, Errors, Pagination, Completions.

Output

Follow any instructions already given to you and your understanding of the current codebase to generate code that solves the objective while maintaining coherence with the current codebase and any previous instructions. You've been provided an example below that is specific for the Deno runtime simply as an illustration and inspiration for your own design. When you're finished the code, create a task in the local package manager configuration that can run this server locally in a development mode.

Implementing Component Examples

NOTE: If you've been provided no instructions of what the first components should be to implement in the MCP server, than generate a very simple stubbed out example of each: Resource, Prompt, Tool, Notification, Error, Pagination, Completion. Please them in a seperate folder, and have them implemenet an abstract base class that is stubbed out with everything the interfaces and types of @modelcontextprotocol/sdk allows for each.

Read the full file on GitHub · 105 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. yesterday First seen · 105 lines · 0 tokens per session scan A 58c4e5145446

Subscribe to this mod's changes

create-mcp-server is a cursor rule published in the GitHub repository zackiles/deno-kit (3 stars, last pushed 5mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,368 tokens. A static security scan graded it A with 0 findings. It is 100% identical to create-mcp-server, differing in 202 lines, and is treated as a copy.