breach_stats

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

Annotations already declare readOnlyHint and idempotentHint. The description adds valuable behavioral context: 'Aggregate counts only; no leaked records' clarifies data granularity, and the mention of the five largest incidents sets output expectations. This goes beyond annotations and does not contradict them.

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 moderately sized and well structured: a clear main purpose statement followed by a list of aggregation axes and example use cases. The examples are useful but slightly redundant; every sentence still earns its place, so it does not drop below 4.

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?

With no output schema, the description explains the result type (incidents and accounts exposed counts) and explicitly states that no leaked records are returned. It does not specify output formatting or pagination, but for a read-only stats tool with strong annotations and a simple parameter set, it is sufficiently 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?

The input schema covers both parameters (sector and group_by) with descriptions and allowed values, achieving 100% coverage. The description restates the group_by options in natural language and gives usage examples, but adds no new parameter-level detail beyond what the schema already provides. Thus 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 opens with a specific verb and resource: 'Aggregate the full breach archive into analyst-grade statistics.' It enumerates distinct aggregation axes (year, source, data_type, threat_level, actor) and mentions the five largest incidents, clearly differentiating it from siblings like breach_timeline or check_exposure.

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 concrete example questions ('how has breach volume trended since 2015', 'which ransomware groups have the most victims') that signal when to use the tool. It does not explicitly name alternative tools or state when not to use it, so it falls short of a 5.

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