vpn_require_active

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The readOnlyHint annotation already indicates a safe, side-effect-free operation. The description adds behavioral context by disclosing that the tool fails when the VPN is not connected, which is beyond the annotation. It does not detail the exact failure mode but provides essential gating behavior.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, concise sentence that immediately conveys the tool's function without any filler. It is perfectly front-loaded and easy to parse.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a zero-parameter assertion tool with a read-only annotation, the description is contextually complete. It tells the agent exactly when it fails (when VPN is not connected) and implicitly when it passes. No output schema or return value details are necessary for this simple guard behavior.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With zero parameters, the baseline score of 4 applies. There is no parameter information to add, and the description is not required to compensate for any missing schema details.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's function: it fails unless NordVPN is connected. The verb 'fail' and resource 'NordVPN' make the purpose unmistakable, and it is clearly distinct from siblings like vpn_status (which reports status) and vpn_connect (which establishes a connection).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The usage is implied as a guard for operations requiring an active VPN, but the description does not explicitly say when to use it versus alternatives like vpn_status, nor does it mention exclusions or prerequisites. There is no alternative guidance, so it only meets the 'implied usage' level.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.