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

readOnlyHint already covers the safety profile, so the description's added value is in disclosing the returned payload, including the crypto_payment.send_exactly detail for stablecoin invoices. It stops short of noting auth needs or behavior for missing/nonexistent invoices.

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?

A single dense sentence that front-loads the core action and enumerates return content without any filler. Nothing 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 explaining returns and does so reasonably well by naming line items, client, payment status, and crypto payment fields. It could go further on error behavior or how missing invoices are handled, but it is adequate for a single-id read.

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?

Only one parameter (invoice_id, uuid), which is self-explanatory and needs little elaboration; the description adds no format or lookup semantics beyond what the schema conveys. Baseline 3 is appropriate for a single obvious identifier.

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") and enumerates what is returned: line items, client, payment status, and stablecoin payment details. It is clearly distinguishable from list_invoices by the singular scope, though it does not explicitly name siblings like get_invoice_passport or get_efactura_xml.

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 by the name and the "one invoice" phrasing; there are no explicit when-to-use or when-not conditions, and no pointer to the sibling tools an agent should prefer for lists, passports, or XML output.

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