get_isbn

THE RISK

Low Risk

Why get_isbn needs a policy

This tool retrieves read-only data about books based on ISBN input. It performs a search/query operation typical of a Read category tool. The server context (AP2 payment protocol) is irrelevant to this specific tool's function. No data is modified, deleted, or financial operations are triggered by this lookup.

From the tool's definition Tool name is 'get_isbn' and description states 'Look up book information by ISBN' — a pure lookup/query operation with no side effects.

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

POLICY

How to control get_isbn

PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for get_isbn:

policy.json

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

get_isbn 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 Ap2 — 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 Ap2 tools

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All 1300 Mcp Ap2 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 get_isbn

What does the get_isbn tool do? +

Look up book information by ISBN. It is categorised as a Read tool in the Mcp Ap2 MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get_isbn? +

Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for get_isbn: 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 Ap2. Nothing to install.

What risk level is get_isbn? +

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

Can I rate-limit get_isbn? +

Yes. Add a rate_limit block to the get_isbn 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 get_isbn completely? +

Set action: deny in the PolicyLayer policy for get_isbn. 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 get_isbn? +

get_isbn is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Ap2 tool call.

Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →