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

With no annotations, the description must disclose behavioral details, but it only mentions billing per call. It does not state whether the operation is read-only, what data source backs it, whether parameters are truly optional, or what the response format will be. The billing note is a small operational detail, but the behavioral burden is largely unmet.

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 short and front-loaded, but the first word merely repeats the title, and the only substantive content is the billing note. This is under-specification rather than efficient completeness.

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 tool with three parameters, no annotations, and no output schema, this description is inadequate. It does not explain return values, data shape, expected behavior, or how it relates to sibling tools like get_v3_website_analytics or get_v2_filter_options. An agent cannot reliably decide when to invoke it or what to expect from the response.

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%, so the baseline is 3 even though the description adds no parameter-level details. The input schema already documents type, country, and platform, including references to the Filter Options endpoint; the description adds nothing beyond what the schema provides.

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 "Marketshare Billing per call: 1 Credits" mostly restates the title and adds a billing note; it does not state the tool's function with a verb like 'retrieve' or 'get'. The tool name implies it returns market-share data, but the description itself does not explain what it does or how it differs from sibling metrics tools.

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?

There is no guidance on when to use this tool instead of alternatives such as get_v2_top_browsers, get_v2_top_engines, get_v2_top_platforms, or get_v2_filter_options. The description provides no use cases, prerequisites, exclusions, or context that would help an agent choose between marketshare and other market-data tools.

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