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

Annotations already declare readOnly, idempotent, and closed-world, so safety is covered. The description adds real behavioral context beyond that: the matching rule (substring match, prefix matches ranked first), cross-kingdom scope, and the different result set when the query is empty — all useful for predicting behavior.

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?

A single dense paragraph that front-loads the core action, then the matching rules, then the returned fields, then the empty-query case. Slightly information-heavy for one sentence, but every clause carries weight and nothing is padding.

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 an output schema present, the description needn't describe return structure, yet it still names the key returned fields. It covers both query modes and the matching rule. The only minor gap is silent limits on result count or pagination behavior, which an agent might want to know.

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 the schema already documents the query parameter and the empty-query fallback. The description reinforces the ranking semantics (names starting with the query come first) and reiterates the empty-query meaning, adding modest value over the structured field rather than repeating it verbatim.

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 a specific verb and resource (find players), anchors it to a familiar analogue ('the same search as the shop's gift window'), and spells out what a result contains (account_id, kingdom, alliance tag, AI flag). No sibling tool offers similar lookup behavior, and the description makes that distinct scope obvious.

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?

It states the use case ('to gift') and covers both modes: a text query versus an empty query, which returns personalized suggestions (past giftees, alliance, DMs). It doesn't explicitly exclude alternatives or name other tools, but no sibling overlaps this lookup, so the guidance is effectively complete.

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