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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely new context: the figures are computed server-side from live Fortnox data and cover all pages, telling the agent the result is a complete, freshly derived dataset rather than a paginated raw listing. It does not discuss latency or freshness lag, but with an output schema present that is a minor omission.

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?

Three compact sentences, front-loaded with the metric definition and followed by the example question and provenance. The Fortnox API URL is marginal filler, but the rest earns its place.

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 an aggregate analytics tool with an output schema and fully documented parameters, the description supplies what an agent still needs: what is measured, over what data source, and with full-pagination coverage. Only sibling differentiation is missing.

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 both the optional customer number and the fromdate default (one year back) are already documented in the schema. The description adds nothing about parameters, which is acceptable given the coverage but means it brings no extra semantic value here.

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 defines a specific computed metric set: how late each customer pays relative to the due date, plus the trend (improving/worsening). That is much more precise than the title alone. It does not, however, contrast itself with overlapping siblings such as get_receivables_aging, check_payment_details, or get_payment_list, so an agent must infer the boundary.

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?

An example question ("Vilka kunder betalar sent? Blir någon sämre på att betala?") implies when the tool applies, which is useful. There are no explicit when-not conditions and no routing guidance among the many receivables/payment siblings, so selection remains partly inferred.

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