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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is covered. The description adds useful domain context beyond the annotations: the dataset is bounded at 50 metros, and the index scale is anchored (US average = 100). It does not mention response ordering or size limits, but nothing important is hidden.

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?

Three short sentences, front-loaded with what the tool returns, then how to filter, then when to use it. Every sentence earns its place with no repetition of the schema or title.

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?

Despite no output schema, the description enumerates the returned fields and the index scale, and it explains the tool's position in the workflow relative to compare_cost_of_living. An agent has everything needed to select and 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%, so the baseline is 3, but the description goes beyond it by explaining the two operating modes: no argument returns the full list of 50, and passing a city returns just that metro. That meaningfully clarifies the effect of the optional parameter for an agent deciding how to call it.

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?

States a specific verb (List) and resource (50 supported US metro areas) and enumerates exactly what each entry contains: RPP index, median rent, median home value, median household income. It is clearly distinguishable from siblings like compare_cost_of_living because it is a reference/lookup list, not a comparison.

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?

Explicitly prescribes the workflow: 'Use this to resolve exact city names before calling compare_cost_of_living.' It also states the alternative behavior when the optional city argument is supplied versus omitted, leaving no ambiguity about when to call it or how it feeds the next tool.

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