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

Annotations already declare readOnlyHint=true and idempotentHint=true. The description adds valuable behavioral details beyond those: monthly compounding, end-of-month contribution timing (ordinary annuity), and a concrete worked example with an output value. This is useful context an agent would not otherwise know.

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 tight: one sentence states the core function and returned link, one gives a clarifying example, and one states the annuity assumption. Every sentence earns its place and the most important information is front-loaded.

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 deterministic, read-only calculator tool, the description plus the rich input schema and output schema provide everything needed to invoke it correctly. It covers inputs, the calculation model, the example, and the link return, with no meaningful gaps.

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 covers all 5 parameters with descriptions, defaults, and constraints (100% coverage), so the schema already carries the parameter documentation burden. The description reinforces initial, monthly, rate, and years through its example, but does not add meaningfully beyond the schema.

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 opens with a specific verb ('Project') and a clear resource ('future value of an initial amount plus monthly contributions'), and adds important formula details such as monthly compounding and ordinary annuity timing. It does not explicitly distinguish itself from sibling financial calculators like compare_investments, so it stops short of a 5.

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 implies the appropriate use case: projecting growth of a lump sum plus recurring monthly contributions at a fixed annual return. However, it provides no explicit guidance about when not to use it or which sibling tool might be more appropriate for related calculations.

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