Validates and lints Mermaid diagram syntax across multiple types, including flowcharts, sequence diagrams, class diagrams, and state diagrams, to ensure they render correctly.
Enables automated Mermaid diagram validation within pre-commit hooks to maintain documentation quality and prevent syntax errors from being committed to a codebase.
Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@Mermaid Lint MCP validate this mermaid flowchart: graph TD; A-->B"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
δΈζηζ¬ | English
A powerful tool for validating Mermaid diagrams with both CLI and MCP server capabilities. Perfect for developers, technical writers, and AI assistants who work with Mermaid diagrams.
# Validate a Mermaid file
npx mermaid-lint-mcp lint diagram.mmd
# Validate Mermaid code directly
npx mermaid-lint-mcp lint --code "graph TD; A-->B"
# Start MCP server for AI assistants
npx mermaid-lint-mcp server
# Get help
npx mermaid-lint-mcp --helpNo installation required! The tool will be downloaded automatically on first use.
Related MCP server: Mermaid-Grammer-Inspector
Pre-commit validation: Ensure all Mermaid diagrams in your codebase are valid
CI/CD integration: Add diagram validation to your build pipeline
Documentation quality: Catch syntax errors before publishing docs
Content validation: Verify diagrams render correctly before publication
Error debugging: Get clear error messages for syntax issues
Real-time validation: Validate generated diagrams instantly
MCP integration: Seamless integration with Claude Code, Cursor, Trae, and other AI tools
Automated workflows: Enable AI to self-validate diagram outputs
β Fast Validation: Optimized for speed with browser reuse and local libraries
β Multiple Formats: Support for all Mermaid diagram types
β Dual Interface: Both CLI tool and MCP server in one package
β Error Details: Clear error messages with line numbers and suggestions
β Timeout Control: Configurable validation timeouts
β Zero Config: Works out of the box
No installation needed - just use npx mermaid-lint-mcp directly.
npm install -g mermaid-lint-mcp
# Then use: mermaid-lint-mcpnpm install mermaid-lint-mcp
# Then use: npx mermaid-lint-mcp# Validate a file
npx mermaid-lint-mcp lint diagram.mmd
npx mermaid-lint-mcp diagram.mmd # 'lint' is default
# Validate code string
npx mermaid-lint-mcp lint --code "graph TD; A-->B"
# With custom timeout (5 seconds)
npx mermaid-lint-mcp lint --timeout 5000 diagram.mmd
# Validate with file option
npx mermaid-lint-mcp lint --file diagram.mmd# Start server for AI assistant integration
npx mermaid-lint-mcp servernpx mermaid-lint-mcp --help # Show all commands
npx mermaid-lint-mcp --version # Show versionAdd to your claude_desktop_config.json:
{
"mcpServers": {
"mermaid-lint": {
"command": "npx",
"args": ["mermaid-lint-mcp", "server"]
}
}
}Type | Syntax | Example |
Flowchart |
| Decision trees, processes |
Sequence |
| API interactions, workflows |
Class |
| Object relationships |
State |
| State machines |
ER |
| Database schemas |
Gantt |
| Project timelines |
Pie |
| Data visualization |
Journey |
| User experiences |
Git Graph |
| Version control flows |
... |
| ... |
interface ValidationOptions {
timeout?: number; // Timeout in milliseconds (default: 5000)
}# Set default timeout
export MERMAID_TIMEOUT=10000
# Enable debug logging
export DEBUG=mermaid-lint-mcp{
"isValid": true,
"error": null,
"diagramType": "flowchart"
}{
"isValid": false,
"error": "Parse error on line 8: ...> C E --> F[End ---------------------^ Expecting 'SQE', 'DOUBLECIRCLEEND', 'PE', '-)', 'STADIUMEND', 'SUBROUTINEEND', 'PIPE', 'CYLINDEREND', 'DIAMOND_STOP', 'TAGEND', 'TRAPEND', 'INVTRAPEND', 'UNICODE_TEXT', 'TEXT', 'TAGSTART', got '1'",
"diagramType": "flowchart"
}$ npx mermaid-lint-mcp lint --code "graph TD; A-->B"
π Validating Mermaid diagram...
β
Diagram is valid!
π Diagram type: flowchartSolution: Use npx mermaid-lint-mcp instead of mermaid-lint-mcp
Solution: Increase timeout with --timeout 10000
Solution: Run with appropriate permissions or use npx
MIT License - see LICENSE file for details.
π Documentation
π Report Issues
π¬ Discussions
Mermaid - Create diagrams with text
Mermaid Live Editor - Online diagram editor
Model Context Protocol - AI integration standard
Validate if a Mermaid diagram can be rendered successfully
| Name | Required | Description | Default |
|---|---|---|---|
| code | Yes | Mermaid diagram code to validate | |
| options | No | Validation options |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations provided. The description does not disclose whether the tool actually renders the diagram, checks syntax only, or has any side effects. Ambiguous about what 'validate' entails.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Single sentence, no redundancy. Perfectly concise for a simple validation tool.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
No output schema; description omits return values (e.g., boolean, errors). For a validation tool, the output is crucial and missing from description.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so baseline 3. The description adds no additional meaning beyond the schema fields; the timeout parameter is described in the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool validates if a Mermaid diagram can be rendered successfully, which is a specific verb-resource combination. With no sibling tools, differentiation is not needed.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No guidance on when to use this tool versus alternatives. Absence of siblings does not excuse lack of context like typical use cases or prerequisites.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
With only one tool, there is no ambiguity; the tool's purpose is clear and distinct by default.
The single tool name follows a clear verb_noun pattern (validate_mermaid_diagram), which is consistent and readable.
A single tool for a server named 'Mermaid Lint' feels insufficient; typical linting servers include multiple tools for validation, formatting, and configuration.
The surface is severely incomplete; only validation is provided, omitting common linting operations like reporting, fixing, or configuring rules.
Unclaimed servers have limited discoverability.
If you are the server author, to access and configure the admin panel.
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