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

Annotations already convey read-only, open-world, and idempotent behavior. The description adds valuable context: the return is limited to a signup page and editorial guides, and it discloses the referral commission requirement. This is useful behavioral and policy context beyond the annotations.

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 somewhat long but each sentence adds value: primary output, use cases, explicit exclusions, and commission disclosure. It is front-loaded with the core purpose and avoids filler.

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 single-optional-parameter tool with rich annotations and an output schema, the description fully covers what the tool does, when to use it, what it won't return, and a required disclosure. Nothing essential is missing.

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 description coverage is 100%, including the default value and allowed languages for the 'lang' parameter. The description does not add parameter-level detail beyond what the schema already states, so the baseline of 3 is appropriate.

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?

Description states a specific verb ('Return') and resource ('the NordVPN signup link together with up to four VoyageHacks guides') and details the guide topics. This clearly differentiates it from sibling link tools like get_hotel_links or get_flight_links.

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?

It explicitly lists user intents that should trigger this tool: public Wi-Fi safety, working remotely abroad, geo-blocked streaming, and online banking while travelling. It also clarifies what users should not expect (no live pricing, no server list, no account creation), though it does not name an alternative sibling to route to.

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