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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered. The description adds real context beyond that: the operation is public and requires no key, meaning it can be called before registration — non-obvious and useful. It stops short of describing freshness or aggregation of the depth values.

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?

Very short, but front-loaded with redundant restatements ('Queue depths.' followed by 'WHEN: public queue depths') before the informative sentence. The example 'arena_queue_status {}' is low value for a tool with one optional parameter.

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 values need not be described, and the tool is a simple read with one optional filter. The description covers what it is, when to pick it over the sibling, and its auth posture — sufficient for correct invocation.

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% and there is a single optional parameter, so the schema already documents 'game' and points at arena_join/arena_catalog for valid ids. The description's 'by game/mode' adds only marginal framing and slightly muddies things by mentioning 'mode', which is not a parameter.

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 ('public peek at matchmaking queue depths by game/mode') and explicitly distinguishes it from the sibling arena_queue_wait. However, the opening 'Queue depths. WHEN: public queue depths' restates the title twice before the real explanation arrives, wasting the most prominent slots.

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?

Names arena_queue_wait as the alternative and marks it as 'your ticket', giving the agent a concrete selection rule. The 'WHEN: public queue depths' clause is circular rather than a genuine condition, so the guidance relies entirely on that one sibling contrast.

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