Mermaid Validator

Example Use Cases

• 1

  Validate Mermaid diagram syntax before sending diagrams to users or embedding them in documents.

• 2

  Render Mermaid diagrams to PNG (base64) for display in MCP-compatible clients that do not support SVG.

• 3

  Detailed CLI-level error messages from Mermaid to debug or fix invalid diagrams programmatically.

Description

This MCP server validates Mermaid diagrams using the Mermaid CLI and returns validation results plus a base64-encoded PNG when successful. It exposes a validateMermaid tool via the Model Context Protocol so LLMs and MCP clients can programmatically check and render diagrams. The server runs the Mermaid CLI in a child process to isolate rendering, capture stdout/stderr, and provide detailed error output to help users fix diagrams. Outputs are formatted as text and image content suitable for integration with MCP agents and clients.