The Api.Browse method gives you a list of all methods that you can call via the Web API with the current firmware. This provides you with an overview of all the methods supported by the CPU. No authorization is required for calling the Api.Browse method. Possible error messages: 4 No resources ||...
AI agents call Api-Browse to retrieve information from ThinkPLC-MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Api-Browse is a read-only discovery operation. It returns information about what methods are available on the PLC controller but does not execute any of those methods, nor does it modify any state. The fact that 'no authorization is required' further indicates it is a safe informational query.
From the tool's definition The tool 'gives you a list of all methods' and 'provides you with an overview of all the methods supported by the CPU'. It retrieves metadata about available API endpoints without modifying, executing, or deleting anything.
Documented attack patterns abuse exactly the kind of access Api-Browse gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and ThinkPLC-MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for Api-Browse:
{
"version": "1",
"default": "deny",
"tools": {
"Api-Browse": {}
}
}Api-Browse is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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The Api.Browse method gives you a list of all methods that you can call via the Web API with the current firmware. This provides you with an overview of all the methods supported by the CPU. No authorization is required for calling the Api.Browse method. Possible error messages: 4 No resources || The system does not have the necessary resources to execute the Web API request. Perform the request again as soon as enough resources are available again. It is categorised as a Read tool in the ThinkPLC-MCP MCP Server, which means it retrieves data without modifying state.
Register the ThinkPLC- MCP server in PolicyLayer and add a rule for Api-Browse: 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 ThinkPLC-MCP. Nothing to install.
Api-Browse 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 Api-Browse 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 Api-Browse. 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.
Api-Browse is provided by the ThinkPLC- MCP server (mrwan84/thinkplc-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from ThinkPLC-MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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23 ThinkPLC-MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.