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

readOnlyHint=true already covers the safety profile, so the description's added value is the disclosure that the response is a denormalized aggregate including line items, payments and contact — non-obvious and important for planning. The REST endpoint adds a small amount of traceability. No pagination or error/not-found behavior is mentioned, but little is needed for a read-only single-record fetch.

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 sentences, front-loaded with what is returned before the API detail. The endpoint sentence is borderline redundant but cheap and aids debugging; nothing else is wasted.

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 carries the burden of describing return values, and it does list the embedded resources an agent will receive. For a one-parameter read-only tool this is close to complete; only error/empty behavior is left unspecified.

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 coverage is 100% and there is only one parameter, so the schema already documents 'Record id.' The description adds only that the id is the invoice id via the /finance/invoices/{id} path, which is marginal beyond the schema. 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 ('Get one sales invoice') and enumerates what the record includes (line items, payments, contact). The word 'one' implicitly separates it from kledo_list_invoices and the 'sales' qualifier from kledo_get_purchase_invoice, but neither sibling is named explicitly.

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?

Usage is only implied: 'Get one' signals a single-record lookup by id, which is enough to infer that a list/search call is a different tool. There is no explicit when-to-use, no prerequisite, and no mention of kledo_list_invoices as the alternative when the id is unknown.

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