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

Annotations already declare readOnly/idempotent/non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: the currency is Arena play credits earned by finishing matches, explicitly distinct from Bazaar Credits, and zings carry a 500-credit TEST price with an immediate effect. However, "fire immediately under your name" reads like a mutation effect and sits uneasily against readOnlyHint=true on a zero-parameter call, creating avoidable confusion about side effects.

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?

Front-loaded with the resource name, then a WHEN clause, then the sibling pointer, then an example — a sensible order with no filler sentences. The nested parentheses in the zing clause are dense and make that portion harder to parse than the rest.

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 explained, and the description still tells the agent what the catalog contains (cosmetics plus a zings array) and in which currency it is priced. The only gap is the missing pointer to the purchase tools that consume this catalog.

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?

The tool takes no parameters, so the baseline is 4. The example call (arena_shop_browse {}) correctly confirms that no arguments are needed, which is the only parameter-related information that could add value here.

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?

"Cosmetics shop" plus a concrete item taxonomy (title cards, badge frames, lobby flair) and the zings array make the resource unambiguous, and it explicitly distinguishes itself from bazaar_shop_browse. It stops short of a clean verb+resource statement, though: the zing clause ("bot-bought zings ... fire immediately under your name") drifts into purchase behavior, leaving mild ambiguity about whether this tool browses or buys.

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?

The "WHEN: browse cosmetics" clause gives explicit trigger conditions, and bazaar_shop_browse is named as the alternative for Bazaar Credits, plus a literal example call. What's missing is routing to the actual purchase siblings (arena_shop_buy, arena_zing_buy), so an agent must infer that buying happens elsewhere.

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