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

Annotations already declare readOnlyHint=true, so the read-only safety is covered. The description adds valuable behavioral context beyond that: it specifies what the response contains and, notably, discloses a limitation for Trainer targets ('explicit effect-data limitation'). This gives the calling agent useful expectations without contradicting the 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 description is four tight sentences with no filler: purpose, output, limitation, and input instruction. Each sentence earns its place, and the most important information (what it builds) is front-loaded.

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?

Given there is no output schema, the description does a good job covering return contents and a known limitation. One minor gap is that it strongly implies at least one of query/cardId is needed but the schema marks zero parameters as required; the description could state this requirement more explicitly.

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%, so the parameters are already documented. The description adds real semantic value by indicating that query and cardId are alternatives ('either... or...'), and its examples align with the schema's examples. This clarifies the intended relationship between the two main parameters.

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 uses a specific verb ('Build') and a precise resource: a complete, legal 20-card Pokémon TCG Pocket deck around a chosen card. It also enumerates the output components (archetype, reasoning, limitations, card list), which clearly separates it from siblings like evaluate_deck or trial_deck.

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 usage context is implied by the purpose: use this when you want a deck built around a specific card. It gives input guidance ('Give either a card name... or a gameplay card id') but does not explicitly contrast with sibling tools such as search_cards, evaluate_deck, or trial_deck, nor state when not to use it.

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