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

Annotations already declare read-only, idempotent, non-destructive and open-world, so the safety profile is covered. The description still adds non-obvious behavior: a live-fetch fallback when a board isn't in the database, a default US board, and a plan-limit message returned on rate limit or quota exhaustion. It does not describe row shape or pagination behavior, so it stops short of a 5.

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?

The most decision-relevant facts (one feed type, no keyword, category semantics) are front-loaded, and each subsequent sentence covers a distinct constraint. A couple of sentences reinforce points already in the schema ('Live boards are only available here', 'Returns a plan-limit message'), which costs some efficiency.

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 7-parameter, multi-mode tool with no output schema, the description covers mode selection, fallback fetching, geographic defaults, and error messaging. It is slightly thin on what a returned board row looks like, though it points to the sort-dependent mover fields indirectly.

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 description coverage is 100% and the parameter descriptions are already detailed (valid type list, country applicability, category guidance, window semantics). The description restates the category-type coupling and window values but adds no syntax, format, or edge-case detail beyond what the schema provides, so baseline 3 applies.

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?

Opens with a specific verb+resource ('Live top-trending board for exactly one feed type') and immediately carves out scope ('No keyword'), which separates it from the keyword-lookup siblings. It also names the sibling it is not (get_time_series) and lists the concrete feed families it serves.

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?

Gives explicit routing rules: use sort='rank_change' for climbers vs a prior snapshot, and use get_growth or get_time_series for app history with an Android bundle ID. It also states a hard exclusion ('Live boards are only available here, not via get_time_series'), which is exactly the when/when-not shape an agent needs.

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