vpn-mcp

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

With no annotations provided, the description carries the full disclosure burden. It successfully communicates the authentication requirement (paid account), but omits other behavioral traits such as network latency implications, caching behavior, rate limits, or specific error conditions (e.g., what happens without an account).

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 consists of two efficient sentences with zero waste. The first sentence establishes purpose, the second states prerequisites—earning their place with high information density.

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 an output schema, the description should ideally elaborate on return structure (e.g., array of objects with region fields). While 'with regions' hints at the payload, it lacks definitive structure guidance, leaving a gap for a tool where the description must compensate for missing output schema.

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 and 100% schema coverage (vacuously), the baseline score of 4 applies. There are no parameters requiring semantic clarification beyond the empty schema.

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 specific action ('List') and resource ('VPN exit nodes with regions'), establishing a distinct purpose from action-oriented siblings like 'vpn_connect' or 'vpn_switch'. However, it does not explicitly differentiate from 'vpn_fetch', which could also imply retrieval of node information.

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 description provides a critical prerequisite ('Requires an active (paid) account'), establishing an eligibility constraint. However, it lacks explicit workflow guidance (e.g., 'use this before vpn_connect to select a node') or explicit alternatives/when-not-to-use relative to sibling tools.

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