Base rates of a property

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

With no annotations, the description carries the burden of behavioral disclosure. It reveals that the tool reports both the objects carrying the field and the whole scope, and divides by the former—an important detail about how results are computed. It also mentions the listing behavior when field is omitted. However, it doesn't explicitly state whether the output is a percentage, count, or other format, though the described division implies proportions.

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 two sentences long and front-loads the core purpose. Every clause serves a purpose: defining the tool, giving when-to-use guidance, explaining the calculation, and noting the field-omission behavior. No redundant or filler content.

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 no output schema, the description adequately explains what the answer reports (both scopes and the division). It also covers the alternative use of omitting field. It doesn't mention the default limit (in schema) or return format details, but given the tool's simplicity and high schema coverage, this is sufficient for an agent to invoke it correctly.

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%, with all parameters described in the schema. The description adds limited new parameter-specific meaning; it reinforces the 'omit field' behavior already in the schema. It does not elaborate on the type or limit parameters beyond what the schema provides, so it meets the baseline for high schema coverage without adding significant extra value.

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 immediately states the tool's function: 'How common each value of a property is.' This is a specific statistical/resource-scoped purpose that clearly differentiates it from sibling tools like search_objects or rankings. It also explains the nuanced behavior of dividing by the number of objects carrying the field, making the purpose unmistakable.

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 explicitly instructs when to call the tool: 'Call it before concluding that a shared trait is meaningful.' It explains why by noting that 'most properties are recorded for only part of the objects' and how the answer handles this. It also clarifies the alternative usage of omitting field to list queryable fields, giving clear context for use.

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