add-tool

add-tool is a skill for Claude Code from cyanheads/socrata-mcp-server. It costs 35 tokens per session (18,494 once invoked), scanned A, a copy of add-tool, Apache-2.0.

A scaffold for adding an MCP tool, a callable function that an MCP server exposes to other software. It follows the project's existing file and registration conventions.

In plain words
What is it for?
Use it when creating a new server capability, defining its inputs and outputs, registering it with the application, and running the project's checks.
Why use it?
It gives a consistent place and structure for new tool definitions and includes a development check for catching implementation or formatting problems.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: mentions Claude Code.

Part of the socrata-mcp-server plugin — 33 skills, 1 MCP server shipped together

Good fit Use it when creating a new server capability, defining its inputs and outputs, registering it with the application, and running the project's checks.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/cyanheads/socrata-mcp-server/add-tool
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.

Any agent
npx skills add cyanheads/socrata-mcp-server --skill add-tool
Clone the repo
git clone --depth 1 https://github.com/cyanheads/socrata-mcp-server

Made for: Claude Code.

Or install socrata-mcp-server, the plugin that ships this one along with the rest of its 33 skills, 1 MCP server.

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 add-tool

README.md
[![agentmods](https://agentmods.dev/badge/skills/cyanheads/socrata-mcp-server/add-tool/github.svg)](https://agentmods.dev/skills/cyanheads/socrata-mcp-server/add-tool)
Your own site
<a href="https://agentmods.dev/skills/cyanheads/socrata-mcp-server/add-tool"><img src="https://agentmods.dev/badge/skills/cyanheads/socrata-mcp-server/add-tool/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 add-tool

Your own site · 80×15
<a href="https://agentmods.dev/skills/cyanheads/socrata-mcp-server/add-tool"><img src="https://agentmods.dev/badge/skills/cyanheads/socrata-mcp-server/add-tool.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 35 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 18,494 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00035 $0.18494
Opus 5.5 $0.00014 $0.07398
Sonnet 5.5 $0.00007 $0.03699
Haiku 4.5 $0.00003 $0.01849

Measured today against content hash f19fd10d9330, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

add-tool scanned grade A with 1 finding 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 today.

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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

const articles = await fetch(input.pmids);
Origin

This is a copy

100% identical to add-tool — 35 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.

framework-skills/add-tool/SKILL.md · 926 lines

How it starts

The opening of the file, as written. The whole thing — 926 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Context

Tools use the tool() builder from @cyanheads/mcp-ts-core. Each tool lives in src/mcp-server/tools/definitions/ with a .tool.ts suffix. The standard registration pattern uses a definitions/index.ts barrel that collects all tools into an allToolDefinitions array for createApp(). Fresh scaffolds from init start with direct imports in src/index.ts — the barrel is introduced as definitions grow. Match the pattern already used by the project you're editing.

Steps

  1. Gather the tool's name, purpose, and input/output shape from the user's request — ask only if genuinely absent
  2. Determine if it needs input the caller may not supply — a confirmation, a choice, the client's roots — which makes it a multi-round-trip handler (ctx.requestInput / ctx.inputs, see api-context)
  3. Create the file at src/mcp-server/tools/definitions/{{tool-name}}.tool.ts
  4. Register the tool in the project's existing createApp() tool list (directly in src/index.ts for fresh scaffolds, or via a barrel if the repo already has one)
  5. Run bun run devcheck to verify — it applies Biome's formatting fixes as it runs
  6. Smoke-test with bun run rebuild && bun run start:stdio < /dev/null (or start:http) — the Core services constructed log record must list the new tool in its tools field (the message text shows only counts); if it doesn't, the tool never reached createApp()

Naming

Tools use lowercase snake_case with a canonical server/domain prefix, {server}_{verb}_{noun} by default. Drop the noun only when the verb is a complete action on its own (git_pull, git_status): if {server}_{verb} leaves "…what?" unanswered — search what? connect to what? — the noun is missing. The full rule is the Name row of the design-mcp-server Design table.

Examples: pubmed_search_articles, pubmed_fetch_fulltext, clinicaltrials_find_eligible.

The server prefix is judged on clarity, not length: the brand name or the plain well-known word for the domain both pass (pubmed_, patents_); an abbreviation fails only when it reads as something else out of context (loc_, ct_). A fourth segment is fine when the noun is inherently two words (openfda_search_device_clearances). When a name resists the schema — can't pick a verb, noun feels generic, the verb wants a second word — that's usually a signal the scope is fuzzy; split the tool, rename, or reconsider.

Read the full file on GitHub · 926 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. today Changed · +31 lines f19fd10d9330
  2. 21d ago Changed · +13 lines 8bda9da26197
  3. 1mo ago Changed · +78 lines 95ce1591e082
  4. 1mo ago First seen · 804 lines · 35 tokens per session scan A 5ba100b246b6

Subscribe to this mod's changes

add-tool is a skill published in the GitHub repository cyanheads/socrata-mcp-server (3 stars, last pushed yesterday), licensed Apache-2.0. It adds 35 tokens to every session and 18,494 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). It is 100% identical to add-tool, differing in 35 lines, and is treated as a copy.

Related

Other skills, from other repositories

design-mcp-server

Design the tool surface, resources, and service layer for a new MCP server. Use when starting a new server, planning a major feature expansion, or when the user describes a domain/API they want to expose via MCP. Produces a design doc at docs/design.md that drives implementation.

cyanheads/treasury-fiscaldata-mcp-server · 62 tokens

add-tool

Scaffold a new MCP tool definition. Use when the user asks to add a tool, create a new tool, or implement a new capability for the server.

cyanheads/treasury-fiscaldata-mcp-server · 35 tokens

api-context

Canonical reference for the unified Context object passed to every tool and resource handler in @cyanheads/mcp-ts-core. Covers the full interface, its RequestContext base, all sub-APIs (ctx.log, ctx.state, ctx.requestInput, ctx.inputs, ctx.clientCapabilities, ctx.enrich, ctx.content), and when to use each.

cyanheads/treasury-fiscaldata-mcp-server · 84 tokens

api-errors

McpError constructor, JsonRpcErrorCode reference, and error handling patterns for @cyanheads/mcp-ts-core. Use when looking up error codes, understanding where errors should be thrown vs. caught, or using ErrorHandler.tryCatch in services.

cyanheads/treasury-fiscaldata-mcp-server · 54 tokens

api-linter

MCP definition linter rules reference. Use when bun run lint:mcp or bun run devcheck reports a lint error or warning (format-parity, schema-is-object, name-format, server-json-, etc.) and you need to understand the rule, its severity, and how to fix it. Every rule ID the linter emits has an entry in this doc.

cyanheads/treasury-fiscaldata-mcp-server · 86 tokens

api-canvas

DataCanvas primitive reference — a Tier 3 SQL/analytical workspace for tabular MCP servers, backed by DuckDB. Use when registering tables from upstream APIs, running ad-hoc SQL across them, and exporting results. Covers the acquire → register → query → export flow, per-table TTL, the token-sharing pattern for…

cyanheads/treasury-fiscaldata-mcp-server · 85 tokens