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

Annotations already declare readOnly/openWorld/non-destructive, so the description is free to add real behavioral context: the data source (batru.gg match aggregation), best-first sort order, the semantics of empty rank (all ranks combined, LoL pre-filtered to Diamond+), and the meaning of `total_matches` as the sample behind the ranking. It even instructs the agent to surface the citation/source_url, which is not derivable from annotations.

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 core purpose is front-loaded in the first sentence, then args, then output/citation guidance — a logical order. It loses a point for re-listing the game enum and rank brackets that the schema already documents, which is mild redundancy rather than waste.

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 still covers the essentials an agent needs: source provenance, sort order, sample-size field, and the citation requirement for presenting results. Nothing material is missing for correct invocation or reporting.

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 100%, so baseline is 3, but the description adds value beyond the schema: it notes that rank words like 'oracle' or 'eternus' also resolve, and it defines `total_matches` as the ranking sample size rather than just a row count. The game and rank enumerations are largely duplicated from the schema, which caps it below 5.

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 verb+resource ('current-patch tier list' of 'best heroes right now') and enumerates the four supported games, which lets an agent separate it from siblings like get_ban_rates, get_hero_momentum or predict_winrate without opening a schema. It also adds the meaningful qualifier that rankings are empirical match aggregation, not a guess.

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?

Clear on when this applies (current best-hero rankings for a given game/patch) and how to scope it with `rank` and `limit`. It does not explicitly route the agent away from siblings or state when-not to use it (e.g. 'use get_ban_rates for ban data'), so it falls short of the explicit-alternatives bar.

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