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

Beyond the readOnlyHint/idempotentHint/destructiveHint annotations, the description explicitly discloses that the tool does not change page or account state, does not access BetterOff customer data, and does not provide personalized financial advice. This gives an agent concrete behavioral boundaries that the structured annotations alone do not convey.

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 three focused sentences: a one-sentence overview, a one-sentence functional summary, and a one-sentence safety/data boundary. It is front-loaded with the most important classification ('Read-only educational calculator') and contains no filler or repetition.

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 calculator with a nested subscriptions array and an output schema, the description covers the high-level behavior, what inputs are used ('caller-supplied public inputs'), and the key safety/privacy boundaries. It is slightly incomplete only because it does not clarify how the two opportunity-cost parameters influence the computation, but the output schema and annotations carry much of the remaining context.

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 only 33%, and the top-level numeric parameters opportunityReturnPct and opportunityHorizonYears have no descriptions. The prose adds some context by tying subscriptions and mixed intervals to the calculation outcomes, but it does not explain what the two opportunity parameters mean or how they affect the future-price scenarios, leaving the agent to rely on guessing from names.

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 uses a specific verb-resource combination: 'Normalizes mixed-interval subscriptions into monthly-equivalent costs... ranks by impact, and computes triage savings, category totals, and future-price scenarios.' This makes the tool clearly distinguishable from sibling calculators such as calc_compound_interest or calc_mortgage without needing to open the schema.

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 phrase 'Read-only educational calculator' and the explicit exclusion of personalized financial advice imply it should be used for educational subscription-cost estimates. However, the description never explicitly states when to prefer this tool over sibling calculators or provides any when-not/alternative routing guidance.

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