AI agents call readme 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 serves an informational purpose—providing documentation or help text about the Mermaid MCP server. It retrieves static information without creating, modifying, executing, or deleting any data or operations. This clearly falls under the Read category with low severity.
From the tool's definition Tool name 'readme' and description 'about this tool' indicate retrieval of documentation or information about the Mermaid server. No side effects, modifications, or external operations are performed.
Attacks that exploit this kind of access
about this tool. 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 readme: 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.
readme 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 readme 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 readme. 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.
readme 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.
Teams ship this data inside their own products. See what a licence covers →