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

The annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world scope, so the safety profile is fully covered by structured data. The description adds genuinely useful model detail: both paths receive identical capital and monthly amounts, the four Swedish rules (amorteringskrav, ränteavdrag, capital gains/mäklararvode, ISK schablonskatt), and differing one-time costs by property type. However, it does not describe the response structure's magnitude or any limits on the calculation horizon beyond what the schema says, so it sits at a solid but not exceptional level given annotation coverage.

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 trigger conditions are aggressively front-loaded and every section carries content an agent needs: triggers, methodology rationale, rules, output handling, units, scope limits. It is nonetheless a long block for a calculator tool, and the methodology paragraph could be compressed without losing instruction value.

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 15 optional parameters, an output schema present and full annotation coverage, the description supplies everything else an agent needs: when to call, the modeling logic to explain to the user, the required presentation of the svar field and lankAttVisaAnvandaren link, unit conventions, and geographic/temporal scope (Sweden, 2026 rules).

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 baseline is 3, but the description adds a cross-parameter convention the schema does not state globally: interest rates and returns are given as 2.7 for 2.7%, not 0.027 — a real source of invocation error. It also explains that propType drives the one-time cost treatment, reinforcing the enum's meaning.

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 precise trigger and resource: someone considering buying a home in Sweden wondering whether it pays off, and quotes the exact user phrasings it handles. It also frames the tool as a net-worth comparison rather than a monthly-cost comparison, which sharply separates it from loan-cost or savings siblings like blancolan_total_kostnad and sparmal_isk_vs_sparkonto.

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?

It states explicitly when to invoke the tool ("när någon överväger att köpa...") and lists four literal user questions that select it. It also gives a clear negative instruction — don't do the monthly-cost comparison yourself — and closes with explicit exclusions: no lånelöfte, no creditworthiness, no price fairness assessment, no non-Swedish tax systems.

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