Find sales invoice by invoice number

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

The annotations already provide readOnly, idempotent, and non-destructive hints, so the description does not need to re-state those. It adds useful behavior beyond annotations: drafts have no invoice number and will never be returned by this lookup, which is valuable for expectation setting.

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, no filler, and the key information is front-loaded: what the tool looks up and by which key. The example is compact and the caveat about drafts is placed at the end without diluting the core message.

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 simple read-only lookup tool, the description together with the annotated hints and well-covered schema is fully sufficient. The absence of an output schema is acceptable because the tool's purpose is straightforward and no return-value description is required when the output schema is absent.

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 the baseline is 3. The description reinforces that invoice_id is the printed document number and provides an example format ('2025-0001'), which adds slight value, but the schema already clearly defines the parameter. No significant compensation is needed.

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?

The description clearly identifies the exact resource (sales invoice) and the lookup key (printed invoice number), with a concrete example. The 'Drafts have no invoice number and are never found this way' qualifier distinguishes this from tools that work with drafts or internal IDs, so it differentiates from sibling lookup tools.

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 implies when to use the tool: when you have the printed invoice number. It also states a clear exclusion, drafts are never found this way. It does not explicitly name alternative tools or conditions that would route to get_sales_invoice vs find_sales_invoice_by_reference, so it misses the top tier but provides solid context.

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