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

With no annotations, the description carries full burden and meets it: it discloses partial-month cutoff semantics, 12-month rolling-window bounds, ranking nature, and absence behavior. It also notes rolloff behavior for older months across all tools, which is valuable operational context.

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 dense and front-loaded with its core purpose in the first sentence, and every sentence contributes. It is a bit longer than necessary and repeats the 12-month-window idea, so it narrowly misses a 5.

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 two-parameter list tool with no annotations and no output schema, the description covers source, scope, ranking, window bounds, partial-month behavior, default behavior, and cross-tool routing. Nothing critical is missing for correct invocation.

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 baseline is 3; the description adds meaning by explaining that the month is a data cutoff with partial-month consequences and by confirming default limit/top-10 behavior. It slightly confuses by using the term 'as_of' for the 'month' parameter, which is the only notable gap.

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 and resource: 'Top-selling car models (and variants) in Denmark for a given month' from bildata.io's monthly top-50 passenger-car statistics. It also names the sibling it is not, saying a model outside the top 50 must be handled by get_model_stats, so an agent can disambiguate immediately.

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 states default usage ('Default: latest month, top 10'), gives an alternative for out-of-top-50 lookups ('look that one up by name with get_model_stats'), and rules out arbitrary past months ('A month OLDER than the window cannot be answered by any tool on this server'). This is explicit when-to-use and when-not-to-use guidance.

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