validateDiagram

THE RISK

Low Risk

Why validateDiagram needs a policy

This tool only performs validation checks on diagram syntax and returns error messages and suggestions. It does not create, modify, delete, execute code, or move data. It is a pure read/analysis operation that examines input and provides informational output without altering any state or triggering external operations.

From the tool's definition Tool name 'validateDiagram' and description 'Validate Mermaid diagram syntax and provide detailed error messages and suggestions' indicate a syntax validation and analysis function with no side effects.

Documented attack patterns abuse exactly the kind of access validateDiagram gives an agent:

POLICY

How to control validateDiagram

PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Mermiad, and nothing reaches the server without passing your rules. This is the rule we recommend for validateDiagram:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "validateDiagram": {}
  }
}

validateDiagram is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Mcp Mermiad — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Mcp Mermiad tools

Write convertDiagram Convert diagram to different formats. Currently supports SVG (PNG/PDF coming soon). Write createCustomTemplate Create a custom template from diagram code for reuse in current session. Write generateDiagram Generate and render a Mermaid diagram to SVG file. Supports all 22+ diagram types with adv Read getDiagramInfo Analyze diagram code and return metadata (type, complexity, node/edge count, estimated ren Read getTemplate Get a specific diagram template by ID with complete code and metadata. Read listSupportedTypes List all supported Mermaid diagram types (22+ types including flowchart, sequence, class, Read listTemplates List available pre-built diagram templates (50+ templates) by category or type. Read searchTemplates Search templates by keyword (name, description, type, tags, or code content).

All 9 Mcp Mermiad tools →

Read tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about validateDiagram

What does the validateDiagram tool do? +

Validate Mermaid diagram syntax and provide detailed error messages and suggestions. It is categorised as a Read tool in the Mcp Mermiad MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on validateDiagram? +

Register the Mcp Mermiad MCP server in PolicyLayer and add a rule for validateDiagram: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Mcp Mermiad. Nothing to install.

What risk level is validateDiagram? +

validateDiagram is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit validateDiagram? +

Yes. Add a rate_limit block to the validateDiagram rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block validateDiagram completely? +

Set action: deny in the PolicyLayer policy for validateDiagram. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides validateDiagram? +

validateDiagram is provided by the Mcp Mermiad MCP server (narasimhaponnada/mermaid-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Mermiad tool call.

Start from Mcp Mermiad, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →