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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's real contribution is that the figures are computed server-side from live Fortnox data and aggregated over all pages. That tells the agent it is pre-aggregated and needs no pagination loop, which is useful context not present in structured fields.

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: purpose first, then an example question, then provenance. The example is somewhat illustrative rather than load-bearing, but nothing is padded and the key claim is front-loaded.

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 one-optional-parameter read tool with an output schema and rich annotations, the description supplies everything an agent needs to select and call it: what it returns conceptually, that it is live data, and that it spans all pages. Only sibling disambiguation 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?

There is a single optional date parameter with 100% schema description coverage, and the schema already explains the YYYY-MM-DD / YYYY-MM forms and the default of today. The description adds no syntax, timezone, or interpretation detail beyond that, so the schema-baseline of 3 applies.

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 names the resource and the shape of the output ('förfallet per intervall och per kund' – overdue by bucket and by customer), which lets an agent distinguish it from the payables counterpart. It never explicitly names get_payables_aging as the sibling it is not, so it stops short of a 5.

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, via an example question about how much is overdue, how old it is, and which customers account for most of it. There is no explicit when-to-use, when-not, or routing to adjacent tools such as get_payables_aging or list_due_dates, which overlap on due-date information.

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