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

Annotations already establish that this is a read-only, idempotent, non-destructive, closed-world calculation. The description adds useful context beyond annotations: it lists the return fields, mentions chart_hints rendering directives, and clarifies that senaro-charts renders locally over stdio only.

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 short and efficient, but it front-loads legal disclaimers before the primary purpose statement. The remaining sentences are concise and each supports selection or invocation, though the chart_hints rendering detail is secondary.

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 calculation tool with a fully described input schema and rich annotations, the description covers outputs, chart_hints behavior, and the local rendering constraint. No output schema exists, but the description compensates by naming the returned values.

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 input schema fully documents all parameters. The description adds no additional parameter meaning beyond what the schema provides, making the baseline score of 3 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 clearly identifies this as a standard compound interest calculator and lists the outputs (future value, contributions, interest, EAR, milestones). It is specific about the resource and calculation type, though it does not explicitly differentiate itself from the many sibling financial calculators.

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 provides no guidance on when to use this calculator versus alternatives such as payoff_vs_invest or calculate_opportunity_cost. It only includes a general disclaimer ('Calculation, not advice') and no use-case context or exclusions.

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