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/mailchimp-mcp-server --skill api-canvasgit clone --depth 1 https://github.com/cyanheads/mailchimp-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/mailchimp-mcp-server/api-canvas)<a href="https://agentmods.dev/skills/cyanheads/mailchimp-mcp-server/api-canvas"><img src="https://agentmods.dev/badge/skills/cyanheads/mailchimp-mcp-server/api-canvas/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/mailchimp-mcp-server/api-canvas"><img src="https://agentmods.dev/badge/skills/cyanheads/mailchimp-mcp-server/api-canvas.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 | $0.00085 | $0.10180 |
| Opus 5.5 | $0.00034 | $0.04072 |
| Sonnet 5.5 | $0.00017 | $0.02036 |
| Haiku 4.5 | $0.00009 | $0.01018 |
Grade A, and why
api-canvas 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 4d 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 api-canvas — 27 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 — 593 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Overview
DataCanvas is a primitive for storage stashes, canvas computes. The existing IStorageProvider is a key/value abstraction — it can stash blobs but exposes no analytical surface. DataCanvas is the analytical surface: register tabular data from upstream APIs, run SQL across multiple registered tables, and export results as CSV/Parquet/JSON.
Tier 3 — @duckdb/node-api is an optional peer dependency (bun add @duckdb/node-api). Servers that don't enable canvas pay zero install cost. Lazy-loaded on first use.
Disabled by default. Set CANVAS_PROVIDER_TYPE=duckdb to enable. Otherwise core.canvas is undefined.
Cloudflare Workers: unsupported. DuckDB has no V8-isolate build. Setting CANVAS_PROVIDER_TYPE=duckdb on a Worker fails closed with a ConfigurationError at init time.
When canvas earns its keep
Two gates before wiring canvas in — both must be yes. Canvas that fails either is a SQL surface nobody queries.
- Is the data analytical, not just large? Canvas is for tabular/numeric result sets an agent runs SQL over — aggregate, group, join, time-series filter. A discovery/search surface returning categorical metadata (titles, IDs, types, dates) where the workflow is find the record, then drill into it does not qualify, regardless of row count. A 5,000-row search result is still discovery. The gate is shape, not size: the right question is "would an agent write
SELECT … GROUP BYagainst this?", not "does it have many rows?" For name→ID resolution over a bounded list, reach for MCP-side list filtering (see thedesign-mcp-serverskill) instead. - Is it too big to inline? A result that fits the response (≤ ~100 rows of compact data) just gets inlined — no canvas. Canvas is the third option only when shape and size both call for it.
If canvas earns its keep, it carries an obligation: a tool that emits a canvas_id MUST ship a dataframe_query tool in the same server's surface (see the simple-shape Tools row and the Checklist). A canvas_id with no query tool is dead output — the agent literally cannot reach the staged data.
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.
- 4d ago Changed · +7 lines ccd12b0799e3
- 7d ago Changed 21b3b7bd133a
- 21d ago Changed · +9 lines 9332c0d732ef
- 28d ago Changed · +21 lines b7ea375ffd05
- 1mo ago First seen · 556 lines · 85 tokens per session scan A a15da8c76763
api-canvas is a skill published in the GitHub repository cyanheads/mailchimp-mcp-server (2 stars, last pushed yesterday), licensed Apache-2.0. It adds 85 tokens to every session and 10,180 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to api-canvas, differing in 27 lines, and is treated as a copy.
Other skills, from other repositories
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…
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.
add-export
Add a new subpath export to the @cyanheads/mcp-ts-core package. Use when creating a new public API surface that consumers import from a dedicated subpath (e.g., @cyanheads/mcp-ts-core/newutil).
frontmcp-production-readiness
Pre-production audit, hardening, and go-live checklists for FrontMCP servers. Use before shipping to verify security hardening, performance, reliability, and observability, and for target-specific production checklists: Node server (Docker, graceful shutdown, Redis session scaling), Vercel and edge (cold-start…
frontmcp-setup
Use when starting, scaffolding, or organizing a FrontMCP project. Covers creating a new project (CLI scaffold or manual) for Node, Vercel, and other targets; standalone versus Nx-monorepo layout, naming conventions, generators, and dependency rules; composing multiple @App classes, ESM packages, and remote MCP servers…
prism-startup
Activate on the first user turn of every conversation, including greetings. Load Prism context using the user's configured project and quick, standard, or deep depth, then greet the developer by their configured agent name and show the matching recent-session context.