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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), so the bar is lower, but the description still adds a real constraint not present in structured data: the 30-day maximum lookback window. It does not disclose pagination behavior despite a cursor parameter, nor does it say how results are ordered or capped by limit.

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 sentences, zero waste. The primary use case is front-loaded and the exclusion/alternative follows immediately, so an agent scanning the description gets the routing signal before any detail.

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 10-parameter, no-output-schema read tool, the description covers purpose, scope limit, and sibling routing, but leaves pagination (cursor), result-count behavior (limit), and the purpose of context/response_format unexplained. Adequate to call the tool correctly in the common case, but not complete for the full parameter surface.

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?

With 60% schema coverage and 10 parameters, the description contributes meaning for the app/chart split ('per app or home shelf') and reinforces the time-window constraint on since/at. However, cursor, limit, context, and response_format get no treatment in either the description or (for two of them) the schema, so it only partially compensates for the coverage gap. Baseline 3 for moderate coverage is appropriate.

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 names the specific resource (featuring history: when and where apps were featured), its two axes (per app or home shelf), and its time scope (at most 30 days). It also explicitly differentiates from the sibling charts_get, which handles current shelf order. It falls just short of a 5 because the phrasing is grammatically awkward ('need when and where') and never states that the result is a historical timeline rather than a point-in-time snapshot.

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?

Both halves of the routing decision are explicit: 'Use this when you need when and where apps were featured... over at most 30 days' and 'Do not use for current shelf order; use charts_get.' The agent gets a positive trigger, a negative trigger, and the named alternative in two sentences.

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