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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds genuinely useful non-obvious behavior — the absence of filter parameters — which prevents an agent from fruitlessly searching for a filter argument. It also names the underlying endpoint, aiding debugging, though it says little about paging limits or result-size behavior (which the schema carries).

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: what you get, the key constraint with the workaround, and the endpoint. Front-loaded and free of filler; every sentence carries information an agent needs.

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 compensates by enumerating the returned fields, and the annotations cover the safety profile. Combined with fully documented parameters, an agent has what it needs to call this correctly; only the pagination envelope (next_page) is left implicit to the schema.

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%, so page, sort, fields and per_page are all fully documented in the schema, including the leading-minus sort syntax and the next_page handoff. The description's sort example duplicates rather than extends schema content, so baseline 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?

States a specific verb and resource ('List invoices') and enumerates what each record contains (number, total, paid flag, dates, customer), which distinguishes it from the singular servicefusion_get_invoice sibling by implication of plural listing. It does not explicitly name that sibling, so differentiation is only partial.

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?

Gives a concrete usage constraint: the API has no invoice filters, so the agent must sort and page instead, with an example (sort=-date). It stops short of saying when to prefer servicefusion_get_invoice or other retrieval paths, but the key operational guidance is present.

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