An MCP server for working with MermaidJS, using `mmdc`.
Documentation
tech.unravel/mcp-mermaidjs-server
An MCP server for working with MermaidJS, using mmdc.
We create two simple tools:
- save-diagram
- visualize-diagram
Using these tools, a host can create beautiful mermaid-js diagrams by:
- creating an mmd spec and saving it
- then rendering the saved-spec using specific output format and (optionally) CSS (via access to
mmdc)
Usage
Building the Uberjar
1. make clean && make build
Running the MCP server
PRE-REQUISITES: Needs mmdc CLI to be installed.
Some example commands you can try in Claude Desktop or Inspector:
1. Create a MermaidJS Sequence Diagram from this spec:
sequenceDiagram
%% See https://mermaidjs.github.io/sequenceDiagram.html
loop everyday D-2 working days 16:00
ABCD->>DEE: [14:25] BEE (Calculation per TC until ACK becomes OK)
ABCD->>FGG: BEE (Calculation per TC until ACK becomes OK)
Note over ABCD,FGG: D-2 weekdays at 14:25
ABCD->>HII: Projected Authorisations to HII
Note over ABCD,HII: D-2 weekdays at 16:00
end
loop D-1 before deadline at 7:45
HII->>DEE: Submission
Note over HII,DEE: D-1 before deadline
HII->>FGG: Submission
Note over HII,FGG: D-1 before deadline
endBefore running the MCP server
Remember:
1. Replace the full-path to the tech.unravel/mcp-mermaidjs-server Jar with the correct path on your system (i.e. replace /Users/vedang/repo-name below with the correct path)
2. Specify the full-path to mmdc on your system
In Claude Desktop
"mcp_mermaidjs_server": {
"command": "java",
"args": [
"-Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory",
"-Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog",
"-Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector",
"-Dlog4j2.configurationFile=log4j2-mcp.xml",
"-Dbabashka.json.provider=metosin/jsonista",
"-Dlogging.level=INFO",
"-Dmcp.vegalite.mmdc_executable=/Users/vedang/.local/share/nvm/v23.11.0/bin/mmdc",
"-cp",
"/Users/vedang/repo-name/target/tech.unravel/mcp-mermaidjs-server-1.0.0.jar",
"tech.unravel.mcp-mermaidjs-server"
]
}In MCP Inspector
Remember to use the full-path to the tech.unravel/mcp-mermaidjs-server JAR on your system.
npx @modelcontextprotocol/inspector java -Dclojure.tools.logging.factory=clojure.tools.logging.impl/log4j2-factory -Dorg.eclipse.jetty.util.log.class=org.eclipse.jetty.util.log.Slf4jLog -Dlog4j2.contextSelector=org.apache.logging.log4j.core.async.AsyncLoggerContextSelector -Dlog4j2.configurationFile=log4j2-mcp.xml -Dbabashka.json.provider=metosin/jsonista -Dlogging.level=INFO -Dmcp.vegalite.mmdc_executable=/Users/vedang/.local/share/nvm/v23.11.0/bin/mmdc -cp /Users/vedang/repo-name/target/tech.unravel/mcp-mermaidjs-server-1.0.0.jar tech.unravel.mcp-mermaidjs-serverLicense
Copyright © 2025 Unravel.tech Engineering
Distributed under the MIT License
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