ck_get_spending_by_merchant

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

Annotations declare readOnlyHint=true, which already covers the safety profile. The description adds a meaningful behavioural detail: results are aggregated by total debit spend (not credit or net spend) and ordered by merchant. However, it does not disclose other traits like pagination behavior or that the top-N ordering depends on the limit parameter, so it adds only partial context beyond 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 a single, front-loaded sentence with no filler. It communicates the core purpose efficiently and every word contributes meaning.

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 simple read-only aggregation tool with fully documented parameters, the description is nearly sufficient. It states the core behavior and the readOnlyHint provides safety context. The main gap is the absence of any usage guidance or mention of the output format, but the latter is not required since there is no output schema to complement.

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 input schema already provides 100% parameter coverage with descriptions for all four parameters (limit default, partial category filter, date formats). The description does not add significant meaning beyond the schema; the mention of 'top merchants' loosely maps to the limit parameter but is not explicit. Baseline 3 is appropriate.

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 clear action ('Return') and a specific resource ('top merchants') qualified by a specific metric ('total debit spend'). It is not tautological and is distinct from sibling tools like get_spending_by_category or list_transactions, though it does not explicitly name or contrast those alternatives.

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?

No guidance is given about when to use this tool versus alternatives such as get_spending_by_category or list_transactions. The description simply states what the tool does, leaving the agent to infer the appropriate context from the name and schema alone.

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