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.
npx skills add cyanheads/toolkit-mcp-server --skill design-mcp-servergit clone --depth 1 https://github.com/cyanheads/toolkit-mcp-serverWrote 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.
[](https://agentmods.dev/skills/cyanheads/toolkit-mcp-server/design-mcp-server)<a href="https://agentmods.dev/skills/cyanheads/toolkit-mcp-server/design-mcp-server"><img src="https://agentmods.dev/badge/skills/cyanheads/toolkit-mcp-server/design-mcp-server/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.
<a href="https://agentmods.dev/skills/cyanheads/toolkit-mcp-server/design-mcp-server"><img src="https://agentmods.dev/badge/skills/cyanheads/toolkit-mcp-server/design-mcp-server.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00062 | $0.19742 |
| Opus 5.5 | $0.00025 | $0.07897 |
| Sonnet 5.5 | $0.00012 | $0.03948 |
| Haiku 4.5 | $0.00006 | $0.01974 |
Grade A, and why
design-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 11d 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.
This is a copy
100% identical to design-mcp-server — 0 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.
How it starts
The opening of the file, as written. The whole thing — 722 lines — stays where its author put it; the contents beside it link to each section on GitHub.
When to Use
- User says "I want to build a ___ MCP server"
- User has an API, database, or system they want to expose to LLMs
- User wants to plan tools before scaffolding
- Existing server needs a new capability area — two or more tools sharing a new noun or service, or any new upstream source (design the addition, not just a single tool)
Do NOT use for a single tool on an existing noun — use add-tool directly.
Inputs
Gather before designing. Ask the user if not obvious from context:
- Domain — what system, API, or capability is this server wrapping? Or is the server providing internal capability with no external dependency (computation, text/code utilities, in-memory state)?
- Data sources / source of truth — APIs, databases, file systems, external services? Or is the server itself the source (in-memory state, pure computation, local-only utility, embedded model)?
- Target users — what will the LLM (and its human) be trying to accomplish?
- Scope constraints — read-only? write access? admin operations? what's off-limits?
- Deployment — local stdio, hosted HTTP, Cloudflare Workers? The answer gates primitives: DataCanvas and
MirrorServicedon't run on Workers, and a tool that asks the caller for input mid-call needs a stateful HTTP session (see the Client round-trip row in Step 3).
If the domain has a public API, read its docs before designing. For internal-only servers, skip API research and go straight to user goals. Don't design from vibes either way.
Server scope and audience
Before committing to a server boundary, answer: what workflow does this server serve, and who is the audience?
The unit of a server is a user workflow, not an API. A single rich API can earn its own server when the audience is large and the API surface supports a full workflow (PubMed for literature research, SEC EDGAR for financial analysis, Shodan for internet-wide device intelligence). Multiple APIs should collapse into one server when they serve the same workflow from different angles — a "threat intelligence" server that aggregates VirusTotal, AbuseIPDB, and GreyNoise is more useful than three separate servers because the user's goal is "assess this indicator," not "query VirusTotal."
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.
- 11d ago Changed · +1 lines e4748940dfc6
- 18d ago Changed · +27 lines e97d277ea950
- 1mo ago Changed · +17 lines ff2e1fa6875e
- 1mo ago Changed · -37 lines 08d0f2d4ad13
- 1mo ago First seen · 714 lines · 62 tokens per session scan A 27b9a61334d6
design-mcp-server is a skill published in the GitHub repository cyanheads/toolkit-mcp-server (18 stars, last pushed 8d ago), licensed Apache-2.0. It adds 62 tokens to every session and 19,742 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to design-mcp-server, differing in 0 lines, and is treated as a copy.
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.
api-telemetry
Catalog of OpenTelemetry instrumentation built into framework @cyanheads/mcp-ts-core — spans, metrics, completion logs, env config, runtime caveats, custom instrumentation patterns, and cardinality rules. Use when enabling OTel export, adding custom spans or metrics in services, debugging missing telemetry, looking up…
api-mirror
Stand up a persistent, self-refreshing local mirror of a bulk upstream dataset with the MirrorService (@cyanheads/mcp-ts-core/mirror). Use when a server wraps a large or slow API and should query a synced local index (embedded SQLite + FTS5) instead of paginating the live API per request.
gamedev-multiplayer
Use when adding multiplayer or netcode to a game — client-server vs P2P, server authority and anti-cheat, state replication vs RPCs, prediction and reconciliation, lag compensation, plus Godot 4 / Unity NGO / Unreal wiring. NOT single-player gameplay (that is godot, unity, unreal), NOT matchmaking or server hosting…
api-services
API reference for built-in service providers (LLM, Speech, Graph). Use when looking up service interfaces, provider capabilities, or integration patterns.
cmdb-patterns
Create ServiceNow CIs and cmdbrelci relationships, walk upstream/downstream impact, detect orphan/stale CIs, and align discovered CIs with the proper sysclassname hierarchy.