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

Annotations already declare readOnly, idempotent and non-destructive, so safety needs no restating. The description adds genuinely new behavioral facts: the result is paginated one page per call and per-page totals must not be summed via repeated calls – use summarize.all_pages instead. Return shape is covered by the output schema.

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 short sentences, front-loaded with the purpose, then endpoint, then the paging caveat. The API URL is mildly gratuitous but serves as a reference anchor; no sentence is wasted.

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 25-parameter read tool with a nested summarize object and an output schema, the description covers the one thing the schema cannot convey – that results are paginated and how to get cross-page totals. Filter semantics are left entirely to the well-covered schema, which is acceptable.

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 88%, so the schema already documents nearly every filter. The description touches only the nested summarize.all_pages flag and says nothing about how group_by/sum work together or how page/limit/offset interact, leaving it at the high-coverage baseline.

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 verb and resource ("Retrieve a list of orders") and anchors it to the underlying Fortnox endpoint GET /3/orders. It is clearly distinct from list_invoices, list_offers and list_supplier_invoices by resource, though it never names an alternative explicitly.

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?

"One page per call; use summarize.all_pages for totals over every page" gives real guidance on pagination and when to switch to server-side aggregation. There is no guidance on when to prefer this over find_uninvoiced_orders or other sibling order/invoice listings, so usage context is only partially covered.

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