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

readOnlyHint=true already tells the agent this is a safe read, so the description's remaining burden is pagination/return behavior. It adds only the raw API endpoint (GET /Invoices/{page}); it says nothing about paging defaults, result ordering, or how multiple filters combine, which the schema only partially covers.

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 short sentences, with the purpose and filter scope front-loaded. The trailing endpoint reference is mildly useful but is essentially redundant metadata that slightly dilutes the sentence.

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 read-only list tool with a fully documented schema and no output schema, the description covers the essentials: what is returned, the filter axes, and pagination. It omits only secondary details such as default page size, which the schema already supplies.

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%, with 9 parameters fully documented including defaults and the invoiceNumber override behavior. The description merely recaps the same filter categories, adding no format, default, or combination semantics beyond the schema.

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+resource (list sales invoices) and enumerates the filter dimensions, so the agent knows it is a filtered collection read. It does not explicitly distinguish itself from siblings like unleashed_list_sales_orders or unleashed_list_sales_quotes, relying on the resource name to do that work.

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?

There is no when-to-use or when-not-to-use guidance, no mention of when to prefer a filtered list versus a direct lookup, and no prerequisites. The agent must infer usage entirely from the tool name and filter list.

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