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

Annotations already indicate readOnlyHint=true and destructiveHint=false, which covers the safety profile. The description does not add behavioral specifics beyond that, such as what exactly the 'stats' include, whether results are aggregated, or any edge cases. It adds minimal value over the annotations, so a low score is appropriate.

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: 'App volume/count stats for a period.' It is concise, front-loaded with the core purpose, and contains no redundant words. This is an exemplary level of conciseness, matching the efficiency seen in high-scoring examples.

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?

Given only two parameters with clear schema descriptions, read-only annotations, and no output schema, the description is adequate but minimal. It conveys the tool's purpose and domain but does not elaborate on the exact return format or the nature of 'volume/count.' It's sufficient for basic selection but leaves some ambiguity about what the stats represent, so a 3 is appropriate.

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?

Both parameters (start_at and end_at) have clear descriptions in the schema, so schema coverage is 100%. The description mentions 'for a period' which aligns with the parameters, but it does not add syntax or format details beyond what the schema already provides. With high schema coverage, the baseline of 3 is justified.

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 states a specific verb and resource: 'App volume/count stats for a period.' It clearly indicates this tool retrieves aggregate statistics for an app over a time range. While it doesn't explicitly name sibling alternatives, none of the sibling tools are stats-related, so it distinguishes itself functionally. The purpose is clear and not a tautology.

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 provides no guidance on when to use this tool versus alternatives. It does not mention any conditions for invocation, prerequisites, or exclusions. Since there are no other stats tools among siblings, the context might be implied, but the description itself offers no explicit usage direction.

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