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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds what the payload contains (venue counts, this-week new, sources), which is useful, but it says nothing about whether stats are live or cached, how 'this week' is defined, or how large the source list is.

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?

One compact sentence with the resource and returned fields front-loaded and no filler. It is terse to the point of underspecifying, but nothing is wasted.

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 carries the return-value burden and does name the three stat groups, which is the minimum an agent needs. However, definitions of 'new this week' and 'sources', plus any ordering or empty-metro behavior, remain unstated.

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 single parameter has 0% description coverage, but its enum fully enumerates the seven valid metros, so an agent cannot pick an invalid value. The phrase 'for a metro' adds only trivial framing beyond the enum; no format or default guidance is needed here.

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?

Names the resource (metro stats) and enumerates the specific contents: tracked venues, new this week, sources. That distinguishes it reasonably well from search_openings, which returns individual openings rather than aggregate counts, though the description never explicitly contrasts the two.

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?

No statement of when to call this versus search_openings, and no prerequisites or exclusions. The aggregate-vs-listing split is inferable from the nouns, but the description leaves it entirely to inference.

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