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

Annotations already establish readOnlyHint=true, and the description adds meaningful behavioral detail: exact rules checked, the categories of advice returned, and the required ID namespace. This gives the agent a clear picture of what the tool will do 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?

Two focused sentences with no filler. The primary purpose and validation rules come first, followed by the important ID-type constraint. Every sentence adds necessary information.

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?

The description fully enumerates what the tool checks and what advice it returns, which compensates for the lack of an output schema. Both parameters are documented in the schema, and the read-only annotation covers side effects, so nothing essential is missing for an agent to call this correctly.

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 the schema already documents the two parameters. The description adds valuable disambiguation by warning that the tool takes gameplay card ids rather than printing ids, which is critical for correct invocation beyond the schema's brief 'Gameplay card id' label.

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 states a specific action ('Check a 20-card Pokémon TCG Pocket deck against the game's rules') with concrete validation criteria and return categories. It clearly differentiates from siblings like simulate_matchup and suggest_deck by framing the tool as a rules/build-advice evaluator, not a simulator or generator. The 'gameplay card ids, not printing ids' note further distinguishes it from catalog/printing-oriented tools.

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 description clearly implies the tool is for validating a deck and getting build advice, so an agent can infer when to call it. It does not explicitly name alternatives or exclusion conditions, but the return categories and validation scope make the intended use obvious across the sibling toolset.

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