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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds real value beyond them by disclosing what each mode returns (metadata + structured FatturaPA fields vs. the raw XML transmitted to the SDI), which matters given there is no output schema. It omits error behavior, e.g. what happens for an unknown uuid or one not yet sent.

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 tight sentences with the payload description front-loaded and the REST endpoint trailered for agents that map to the API surface. No filler, nothing repeated from the annotations.

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 two-parameter read tool with full annotation coverage and an optional xml mode, the description supplies everything needed to call it correctly, including the meaning of both output shapes. It stops short of covering failure modes or confirming that metadata is included in xml mode, which would close the gap.

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 already documents uuid, format, and the json default, so the baseline is 3. The description earns above baseline by explaining what each format value actually yields – parsed FatturaPA JSON versus the original SDI XML – which the enum alone does not convey.

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 ('One invoice by uuid') and goes further to name what comes back: metadata plus the FatturaPA JSON payload, or the XML sent to the SDI. It does not explicitly distinguish itself from the adjacent acube_get_draft_invoice sibling, so it falls short of a 5.

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: retrieve a single invoice when you have a uuid. There is no explicit when-to-use guidance, no statement of when to prefer acube_get_draft_invoice or the list endpoints, and no mention of format selection heuristics. The 'uuid (from acube_list_invoices)' hint lives in the schema, not the description.

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