get_user_details

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

No annotations are provided, so the description carries the full burden. It explicitly mentions the Viber rate limit of 2 calls per 12 hours per user and advises caching, which is a valuable behavioral disclosure beyond the input schema. However, it does not describe return format, permissions, or side effects.

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 sentence that clearly states the purpose. Every word is useful, and there is no unnecessary content. It is appropriately sized for a simple tool with one parameter.

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?

While the tool is simple with one parameter and no nested objects, the absence of an output schema means the description should explain what profile details are returned. It does not, leaving that information implicit. The description covers the input and rate limit but lacks output information, making it partially complete.

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%, and the schema already includes a detailed description of the 'id' parameter, including the rate-limit note. The tool description adds no additional semantic meaning beyond what the schema provides, so baseline 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?

The description uses a specific verb ('Fetch') and clearly identifies the resource ('profile details of a Viber user'). Among sibling tools, which are primarily messaging and account tools, this description uniquely identifies its purpose and scope.

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 implies the tool should be used to get user details, but it does not provide any context about when to use it versus alternatives, nor does it mention any prerequisites or post-conditions. No guidance on exclusion or alternative tools is given, so it only minimally guides usage.

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