vpn-mcp

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

With no annotations provided, the description must carry the full burden of behavioral disclosure. It compensates by listing the specific data fields returned (payment state, quota, expiry, active node), effectively substituting for a missing output schema. However, it lacks information on caching behavior, rate limits, or authentication requirements.

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?

Two sentences total with zero waste. Front-loaded with the action verb, followed by a colon-delimited list of return values, and concluding with precise workflow context. Every word earns its place.

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?

Given the absence of both annotations and output schema, the description adequately compensates by enumerating the status fields that would be returned. The workflow context (post-payment, pre-connect) completes the picture for a 0-parameter status tool, though an output schema would provide additional completeness.

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?

The input schema contains zero parameters, which per the evaluation guidelines establishes a baseline score of 4. The description correctly does not invent parameter documentation where none exist, and the absence of parameters is appropriate for a simple status retrieval operation.

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 opens with a specific verb+resource ('Check VPN account status') and immediately enumerates exactly what status components are returned: payment state, quota used/remaining, expiry, and active node. This level of specificity clearly distinguishes it from action-oriented siblings like vpn_connect or vpn_activate.

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?

Provides explicit temporal workflow guidance: 'Use after payment to verify activation before connecting.' This establishes the correct sequence relative to payment and connection actions, implicitly positioning the tool between vpn_activate and vpn_connect. Could be improved by explicitly naming sibling alternatives, but the guidance is clear.

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