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

Annotations supply only destructiveHint=true, so the description carries most of the behavioral burden. It contributes the minimum-input rule and the underlying endpoint, but says nothing about permissions, duplicate handling, or what a successful call returns. Useful additions, but well short of full disclosure for an unannotated mutation.

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 fragments, front-loaded with the action and constraint, with zero padding. The trailing endpoint reference is arguably redundant but is cheap and aids traceability.

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 moderate-complexity create tool with no output schema and thin annotations, the essentials (action, contacts support, minimum required input) are covered. The large set of optional fields is left undescribed, which is tolerable only because their names are largely self-explanatory.

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 only 29% across 14 parameters, so the description needs to compensate and largely does not. It touches only 'name' and 'contacts' (mirroring what the schema already says) and leaves fields like address1/address2, id_number, vat_number, public_notes and private_notes with no added meaning.

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 ('Create a client') and adds the notable scope detail that contacts can be created in the same call. It does not explicitly differentiate from the sibling invoiceninja_update_client, but create-vs-update is unambiguous from the name.

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?

Adds a real precondition not present in the schema — 'Give at least a name or one contact' — which matters because the schema declares zero required parameters. However, it names no alternatives (e.g. update_client for existing clients, get_client/list_clients for lookup) and gives no when-not-to-use guidance, so usage is only implied.

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