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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data and the bar is lower. The description adds almost nothing beyond that: it does not state the compounding assumption (annual vs monthly), how the rate is treated, or how contributions are timed, all of which materially affect the projected number.

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?

A single front-loaded sentence that states the core operation first and qualifies it parenthetically, with zero filler words. Nothing in it is redundant with the title or restates fields unnecessarily.

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?

Wait—assessing relative to None.

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% (rate, years, amount, contribMonthly all documented), so the schema carries the parameter burden and a 3 is the baseline. The description contributes one useful hint by marking contributions as optional, but no format, units, or default guidance beyond what the schema already shows.

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?

States a specific verb and resource with scope: 'Project the future value of a lump-sum investment (optionally with monthly additions), including interest earned.' An agent can distinguish it as a projection tool rather than a rate calculator, but it never names the close siblings (compound_interest, simple_interest, rule_of_72) whose scopes overlap, so sibling differentiation is left to inference.

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?

Usage is only implied by the verb 'Project' and the mention of lump-sum plus optional monthly additions. There is no explicit when-to-use, no when-not, and no pointer to compound_interest or simple_interest for simpler scenarios, so an agent must infer routing from the purpose sentence alone.

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