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

Annotations already declare readOnlyHint and idempotentHint, and the description adds meaningful behavioral context: results are cost-optimized, personalized, and include before/after ownership percentages via fromPct/toPct. It does not reveal return structure or data staleness, but the annotations lower the burden and the added context is useful.

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 dense and front-loaded with the core purpose, followed by one clarifying sentence about percentage semantics. It is slightly long but every clause earns its place; no filler or redundant restatement of annotations.

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?

For a tool with only three optional parameters and no output schema, the description gives enough context to understand the recommendation behavior and key output fields. Minor gaps exist: the exact return shape is not described and fromPct/toPct appear without explicit confirmation that they are output fields, but the overall tool is simple enough that the description is nearly sufficient.

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 already documents format and source well, while limit is constrained with defaults but not described. The description adds semantics for fromPct/toPct, but those are not actual input-schema properties, which may confuse parameter mapping. Overall, the description does not substantially compensate for the 67% schema coverage and the undocumented limit 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?

The description states a specific, personalized purchase-advice verb/resource: 'the single cards that move the signed-in user closest to completing current tournament decks per money spent.' It also lists concrete output aspects (copies to buy, cost, decks advanced), which clearly separates it from siblings like price_list or buildable_meta_decks.

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 makes the usage context clear: it is for a signed-in user, based on their existing collection, and oriented to current tournament decks. It does not explicitly name alternatives or say when not to use it, but the context is strong enough for an agent to infer the right scenario.

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