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

With no annotations, the description carries the full behavioral burden. It does add real value by declaring the call is free (no credit cost) and mirroring GET /v1/trends for cross-reference. It says nothing about auth behavior for api_key, rate limits, ordering, or empty-result handling, so significant gaps remain.

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?

Two compact sentences with the core behavior front-loaded and zero filler. The trailing 'Free. Same as GET /v1/trends.' is telegraphic but each fragment carries distinct information, so 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?

An output schema exists, so return shape needn't be explained, and the description covers the gist of the result. But for a tool with an optional api_key and no annotations, it should say more about auth/credit implications and comparison-window mechanics. Adequate but clearly incomplete.

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 only 50%: window has a description listing 7/30/90 days, but api_key is undocumented. The description does not mention either parameter, so it fails to compensate for the uncovered api_key or to clarify window semantics such as whether the comparison period is trailing.

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 resource and behavior: rising words and phrases in the shared index's titles, compared window-over-window, with counts and growth. That is far more informative than the name alone. It does not, however, differentiate itself from plausible siblings such as trending_shorts, search_index, or niche_report, so the agent must infer which to pick.

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?

There is no explicit when-to-use guidance, no exclusions, and no named alternatives among the many trend-adjacent siblings. The window-comparison phrasing hints at trend detection, but the agent gets no rule for choosing this over search_index or trending_shorts.

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