AI agents call list_diagrams to retrieve information from Mermaid without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and returns information about available diagrams without creating, modifying, executing, or deleting any data. It is purely informational and read-only, making it a Read category risk with low severity.
From the tool's definition Tool name 'list_diagrams' and description 'list available diagrams' indicates a retrieval operation with no side effects.
Attacks that exploit this kind of access
list available diagrams, if want to create a diagram, must use the get_diagram abd get_diagram_examples tools to learn about the diagram. It is categorised as a Read tool in the Mermaid MCP Server, which means it retrieves data without modifying state.
Register the Mermaid MCP server in PolicyLayer and add a rule for list_diagrams: 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 Mermaid. Nothing to install.
list_diagrams is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_diagrams 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.
Set action: deny in the PolicyLayer policy for list_diagrams. 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.
list_diagrams is provided by the Mermaid MCP server (mermaid-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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