Agentic Mermaid MCP Server

Install Agentic Mermaid MCP server

claude mcp add agentic-mermaid -- npx -y agentic-mermaid mcp

{
  "mcpServers": {
    "agentic-mermaid": {
      "command": "npx",
      "args": [
        "-y",
        "agentic-mermaid",
        "mcp"
      ]
    }
  }
}

{
  "mcpServers": {
    "agentic-mermaid": {
      "command": "npx",
      "args": [
        "-y",
        "agentic-mermaid",
        "mcp"
      ]
    }
  }
}

{
  "servers": {
    "agentic-mermaid": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "agentic-mermaid",
        "mcp"
      ]
    }
  }
}

{
  "mcpServers": {
    "agentic-mermaid": {
      "command": "npx",
      "args": [
        "-y",
        "agentic-mermaid",
        "mcp"
      ]
    }
  }
}

Context tax

Connecting this server adds ~43,918 tokens of tool definitions to every model turn (bloated, 9 tools). Measured 2026-10-19 via its hosted endpoint; o200k tokenizer, worst case for clients that load all tools up front. How we measure

Input prices as of 2026-10-06. Excludes your own prompt and output.

Tools (9)

• render_png13,185 tok

  Rasterize a Mermaid source string to PNG. Returns { ok, png_base64 }. Hosted rendering uses resvg-wasm with bundled fonts; bytes may differ from the local napi renderer, so hosted PNG is a convenience surface, not part of the byte-determinism contract. For file/URL artifacts use the local stdio server.

• render_svg12,730 tok

  Render a Mermaid source string to themeable SVG. Returns { ok, svg }. Layout is deterministic: identical input produces identical geometry. The hosted boundary forces security:'strict' and embedFontImport:false.

• render_ascii12,653 tok

  Render a Mermaid source string to text. Returns { ok, text }. useAscii true → plain ASCII (+,-,|); false/absent → Unicode box drawing (┌,─,│). targetWidth sets a hard terminal display-cell bound; impossible bounds return a typed error.

• executeshell4,110 tok

  Run JavaScript in an isolated sandbox; return a value. One call composes edits. Submit JavaScript; declaration types are guidance. No promises, async/await, dynamic import, or type annotations. Hosted note: execute runs in an on-demand isolate and costs more than the direct render_svg/render_ascii/render_png/verify/describe tools — prefer those for plain render/verify calls. For straightforward structured edits, prefer the declarative mutate/build tools; reserve execute for logic the ops don't express. Hosted mermaid.renderMermaidSVG*, renderMermaidASCII*, and layoutMermaidWithReceipt calls fo

• mutate285 tok

  Apply a list of structured edit ops to an existing Mermaid `source` and return the edited diagram. This is the declarative counterpart to `execute`: plain JSON in, plain JSON out, no sandbox. Prefer it for straightforward edits; reserve `execute` for logic the ops don't express. Returns { ok, family, source, verify:{ ok, warnings } } on success, or { ok:false, family, opIndex, error } — where `error` names the offending field and lists the valid ones — when an op is malformed or cannot apply. Ops apply in order and are all-or-nothing: the first failing op stops the batch (its position is `opIn

• build200 tok

  Author a new Mermaid diagram from blank by folding a list of structured ops over an empty diagram of `family`. The declarative counterpart to hand-writing source. Returns the same envelope as `mutate`: { ok, family, source, verify } or { ok:false, family, opIndex, error }. Call `describe_sdk` for the family before authoring unfamiliar ops.

• describe_sdk184 tok

  Return version-matched mutation operations for one diagram family. Use detail=signatures for the compact op menu or detail=fields (default) for exact field types, required flags, enum values, defaults, and constraints. Call this before build, mutate, or execute when the family schema is not already known.

• describe142 tok

  Describe a Mermaid diagram. format=text returns { ok, text } with one or two summary sentences; format=json returns { ok, tree } with the AX tree; format=facts returns { ok, facts } with deterministic semantic fact lines for machine checking (for example edge A -> B : label, member Duck +quack()).

• verify141 tok

  Parse and verify a Mermaid diagram without rendering it. Returns { ok, family, summary, warnings, layout: { bounds, nodes, edges } } for valid diagrams and { ok: false, errors } for parse failures. `family` is the detected diagram family and `summary` a one-line description — check them: ok:true only means the diagram is structurally valid, not that it is the kind you intended. Warnings use the layout-rubric codes.

Security signals

100/100 — no known issues found as of 2026-10-19, from the checks below. This is not a guarantee of safety; review what a server can do before connecting it.

Scan it yourself before installing with vectra-guard, the open-source agent security CLI. Scoring rules

Freshness

Active — last maintenance signal today. The newest of the signals below sets the band.

1. Last commit (default branch)

   2026-10-19 · today · GitHub

2. Latest release

   2026-07-31 · 3mo ago · GitHub · v0.4.1

3. Package published

   no data · npm/PyPI

4. Registry entry updated

   2026-07-31 · 3mo ago · official registry · v0.4.1

How it compares in Cloud Platforms

Against the most-starred cloud platforms servers we index. Token cost is per model turn, measured from each server's live tool list.