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

Goes beyond the readOnly/openWorld annotations by disclosing the prerequisite (NordVPN app must be installed on this Mac) and that no sign-in is required because it reads NordVPN's public API. That auth/prerequisite context is exactly what annotations cannot express; only rate limits or failure modes are missing.

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?

Three tight sentences: purpose first, then prerequisites, then return fields. No filler, though the return-field sentence is partly redundant given an output schema exists.

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?

An output schema exists, so enumerating return fields is optional; the crucial operational facts (app dependency, no login, filtering modes) are present. Only sibling disambiguation is missing for a fully complete definition.

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?

Schema coverage is 100%, so type/limit/country are fully documented in the schema. The description only echoes 'by country or specialty' without adding format or defaulting behavior beyond what the schema already states. Baseline 3 applies.

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?

States a specific verb and resource ('Get recommended NordVPN servers') and scopes it to country or specialty. It is clear on its own, but it never mentions how it differs from the sibling nordvpn_status or nordvpn_diagnose, which an agent could easily confuse with a server-listing call.

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?

Usage is only implied: 'by country or specialty' suggests when the country/type params apply, and 'Omit for auto-recommendation' is a hint. There is no explicit statement of when to pick this over nordvpn_status (current connection) or nordvpn_diagnose, and no exclusions.

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