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

No annotations are provided, so the description carries the full burden. It does disclose one genuinely useful behavioral fact: the result contains a calculator_url that should be rendered as a markdown link, which is non-obvious and actionable. However, it says nothing about the shape of the numeric result, the schedule behavior when include_schedule is set, or defaults/limits beyond what the schema already states.

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?

Two sentences with zero filler: the purpose leads, and the output-rendering requirement follows immediately. The IMPORTANT flag correctly draws attention to the one thing an agent could plausibly get wrong.

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?

With no output schema and no annotations, the description is the only place return-value information can live, and it only covers the calculator_url. It omits what the numeric payload looks like and how include_schedule changes the response, which leaves an agent partially blind for a five-parameter financial calculator.

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 every parameter (years, principal, annual_rate_pct, include_schedule, monthly_contribution) is already documented, establishing a baseline of 3. The description's mention of monthly contributions and monthly compounding loosely maps to parameters but adds no syntax, units, or defaults 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?

States a specific resource and scope: future value of an investment with monthly contributions and monthly compounding. This distinguishes it from nearby siblings like calculate_roth_conversion or calculate_retirement_savings_planner, though it never explicitly names which sibling to prefer for overlapping retirement/investment questions.

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 contains no when-to-use or when-not-to-use guidance, and no alternatives are mentioned. The only instruction given is about post-processing the result (showing the URL), which is output handling rather than tool-selection guidance.

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