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

The description is transparent about behavior: it notes that funds with no data are omitted, order is not guaranteed, and values are decimal fractions representing total return with distributions reinvested. These details are essential for interpreting results and are not contradicted by any 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 concise and structured logically: it states the purpose, compares to a sibling, lists key parameters, describes output format, and gives a usage recommendation. Every sentence adds value without unnecessary length.

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 the lack of an output schema, the description provides sufficient context by describing the output (one row per fund, omitted if no data, unordered) and the value format. It covers the main use case and also mentions that order is not guaranteed, which is a common pitfall. It does not cover error handling or edge cases, but those are not strictly necessary for a straightforward batch query tool.

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 description mentions that the caller should pass 'codes' and 'year,' but it does not elaborate on what 'year' means (e.g., calendar year vs. fiscal year, default behavior if omitted). The schema provides detailed descriptions for 'codes' and 'market,' but not for 'year,' so the description adds little beyond the schema for this 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 clearly states it provides calendar-year total returns for up to 100 funds in one call, explicitly distinguishing it from the single-fund sibling getCalendarReturns. The batch nature and specific metric are immediately 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 explicitly says 'Use this to compare funds across a year,' giving a direct use case. It also implies the alternative (single-fund retrieval via getCalendarReturns) by noting 'same data as getCalendarReturns,' which helps an agent choose the right tool.

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