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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is fully covered. The description adds no behavioral context beyond that — no pagination behavior, result caps, ordering defaults, or auth/permission notes — and only restates the endpoint ('GET /invoices').

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, front-loaded with the resource and its fields before the filter list. Dense but readable; the field enumeration earns its place since there is no output schema.

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 no output schema, the description usefully enumerates returned fields (totals breakdown, terms, notes) and the filter surface. Pagination and sort defaults are left entirely to the schema, which is acceptable given its coverage, but nothing ties the pieces together for a first-time caller.

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 67% and the schema already documents top, skip, sort, descending and include_custom_fields. The description contributes the filter set and clarifies status semantics ('prebill or finalized'), but omits the pagination and sorting parameters entirely, adding only moderate value.

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 ('List invoices') and immediately enumerates the record's fields, which cleanly separates it from siblings like bill4time_list_payments or bill4time_list_expenses. An agent can identify both what it returns and what it operates on without opening the schema.

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?

The description names the available filter dimensions (status, paid status, client, project, id, date range), which implies when the tool is useful, but gives no explicit when-to-use/when-not guidance and never points to an alternative sibling. Adequate but leaves routing to inference.

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