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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety is covered. The description adds the useful invariant that exactly one template is default and that it acts as a fallback for invoice creation. It does not disclose pagination behavior, result-count limits, or what the response envelope looks like for what is, after all, a paged list call.

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?

Two tight sentences with zero filler; the field inventory comes first and the default-template rule second. The opening is a noun phrase rather than a clause, which slightly weakens front-loading but costs no space.

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 simple read-only, closed-world list with no output schema, the description covers what is returned well enough to act on, and it explains the one semantic landmine (the default flag). The remaining gap is pagination — with page/per_page present and no output schema, an agent cannot tell whether it is seeing everything.

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 0% and the description mentions neither page nor per_page, so the two parameters are undocumented beyond bare titles and defaults (1 and 50). For a paginated list tool the description should at least state that results are paged and what the default page size implies.

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 clearly identifies the resource (the merchant's customer-invoice templates) and enumerates the fields they carry — company details, bank lines, taxation label and rate, payment terms, mail text — so an agent knows exactly what it is retrieving. It falls short of a 5 because there is no explicit verb and no differentiation from nearby siblings such as list_templates or list_customer_invoices.

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 provides concrete usage context by explaining the default-template invariant and its link to create_customer_invoice: one template has is_default = true and is used when no template is supplied to the create call. That is a real when/why, though it stops short of explicit exclusions or naming alternative tools.

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