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

With no annotations, the description carries the full burden; it does disclose the two behavioral facts that matter most — no cost ('FREE') and a hard limit of 5 stations — but says nothing about forecast horizon, update frequency, or return shape. Partial coverage on a zero-param read tool.

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 that front-loads the cost signal, then the resource, then the scope and source. No filler.

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 no-parameter sample endpoint with no output schema, the description conveys what you get (a WBGT heat-stress forecast) and how much of it (5 stations), which is enough to call it correctly. Only the response format and forecast horizon are left unspecified.

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 tool takes zero parameters, so the schema baseline of 4 applies. Nothing in the description contradicts or needs to supplement the empty input object.

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 concrete resource (WBGT heat-stress forecast), a concrete scope (first 5 stations), and the data source (MoE Japan). 'Sample' plus the station cap makes it distinguishable from wbgt_search and hottest, though it doesn't explicitly name those siblings.

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 leading 'FREE' and the word 'sample' imply this is a low-cost preview to try before using a full/search tool, but no explicit when-to-use or when-to-prefer-wbgt_search guidance is given. Usage is inferable rather than stated.

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