create-mcp-tool

create-mcp-tool is a skill for Claude Code, Codex from nickytonline/mcp-typescript-template. It costs 43 tokens per session (2,818 once invoked), scanned A, original, MIT.

A guide for adding a new tool to an existing Model Context Protocol server template. It specifies where registration, logic, validation, results, typed output, and tests belong.

In plain words
What is it for?
Use it to register tools in src/tools.ts, validate inputs with Zod, format results, define typed output, and add colocated tests.
Why use it?
It keeps each new tool wired consistently and ensures the registered behavior is covered by the server's tests. It also helps avoid differences between production wiring and test wiring.

Skill for Claude CodeCodex

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 skills/nickytonline/mcp-typescript-template/create-mcp-tool
Any agent
npx skills add nickytonline/mcp-typescript-template --skill create-mcp-tool
Clone the repo
git clone --depth 1 https://github.com/nickytonline/mcp-typescript-template

Made for: Claude Code, Codex.

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 create-mcp-tool

README.md
[![agentmods](https://agentmods.dev/badge/skills/nickytonline/mcp-typescript-template/create-mcp-tool.svg)](https://agentmods.dev/skills/nickytonline/mcp-typescript-template/create-mcp-tool)
Your own site
<a href="https://agentmods.dev/skills/nickytonline/mcp-typescript-template/create-mcp-tool"><img src="https://agentmods.dev/badge/skills/nickytonline/mcp-typescript-template/create-mcp-tool.svg" alt="Measured on agentmods" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,818 The whole file, excluding the scripts and references it only reads on demand.
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 $0.00043 $0.02818
Opus 5 $0.00022 $0.01409
Sonnet 5 $0.00009 $0.00564
Haiku 4.5 $0.00004 $0.00282

Measured 5d ago against content hash 6fdba688192d, 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-tool 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 5d 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.

.agents/skills/create-mcp-tool/SKILL.md · 268 lines

How it starts

The opening of the file, as written. The whole thing — 268 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Add an MCP Tool to This Template

This skill walks you through adding a new tool to the MCP server. If you need to reference MCP SDK types, capabilities, or advanced patterns not covered here, use the context7 MCP server or WebFetch to look up the @modelcontextprotocol/server documentation.


Template Conventions

Concern Location
Tool registration src/tools.ts inside registerTools(server) via server.registerTool()
Tool logic src/tools.ts — functions that take only the dependencies they need
Response formatting createTextResult() / createErrorResult() from src/lib/utils.ts
Input validation Zod inputSchema defined inline in server.registerTool()
Typed output outputSchema + structuredContent (emitted automatically by createTextResult)
Tests src/tools.test.ts (colocated with src/tools.ts)

Everything for a tool lives in src/tools.ts. registerTools(server) is the single source of truth for tool wiring — it's called from getServer() in src/index.ts and reused by the tests, so registration can never drift from what's tested. Each tool's implementation is a function that takes only the dependencies it needs (e.g. the bound sendLoggingMessage function and the ctx object), which keeps it small and easy to drive through every branch. index.ts owns only HTTP routing via createMcpHandler — per the MCP 2026-07-28 spec there's no session: getServer() runs fresh for every request.


Step 1: Name the Tool

Tool names should use snake_case — this is the prevailing community convention (e.g. get_user, search_documents, list_items). The MCP spec (SEP-986) allows a-z, A-Z, 0-9, _, -, ., and /, but does not mandate a style. Names must be 1–64 characters and unique within the server.

The tool's description and every Zod field's .describe() are how LLM clients decide when and how to call the tool — write them as if you're explaining the tool to someone who has never seen the codebase.

Read the full file on GitHub · 268 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. 5d ago First seen · 268 lines · 43 tokens per session scan A 6fdba688192d

Subscribe to this mod's changes

create-mcp-tool is a skill published in the GitHub repository nickytonline/mcp-typescript-template (54 stars, last pushed 25d ago), licensed MIT. It adds 43 tokens to every session and 2,818 once invoked, about $0.0002 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 2026-08-30.

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