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

Annotations already declare readOnlyHint=true, so safety is covered; the description adds genuinely new behavioral detail by disclosing the enriched response contents (line items, taxes, discounts, shipping) and the underlying endpoint. No mention of error behavior for an invalid hash_key, which is the only notable omission.

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, both front-loaded with the key information (what is fetched, what comes back), with zero redundant filler.

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 a single fully-documented parameter and no output schema, the description supplies the most important missing piece — the shape of the returned invoice — leaving nothing an agent needs in order to call it correctly.

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 the schema already explains that hash_key is a short string rather than a numeric id. The description names the parameter but adds no format or validation detail beyond the schema, so the 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 invoice by hash_key') and enumerates what the payload includes (line items, taxes, discounts, shipping). It is clearly distinguishable from hiveage_list_invoices, which returns many.

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?

'Get one invoice by hash_key' clearly implies the retrieval scenario and contrasts implicitly with the list_* siblings. It does not explicitly name when to prefer list_invoices or get_payment instead, so it stops short of a full routing instruction.

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