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 genuinely useful context — the upstream API rejects ranges wider than 31 days — but says nothing about result volume, pagination, or whether the last-changed range interacts with the invoice range.

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?

Roughly two sentences, front-loaded with the resource and the hard constraint before the optional filters. The dangling 'GetInvoice.' fragment at the end is noise that earns no place.

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?

Read-only list tool with annotations covering safety and a fully documented schema, so the description only needs to frame the query. It does that, though with no output schema an agent still cannot predict result shape or volume — a minor but real gap for a list endpoint.

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% and the schema already documents each field's format and the 31-day rule, so the baseline is 3. The description restates the date constraints from the schema rather than adding new meaning, and the trailing 'GetInvoice.' token contributes no semantic value.

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 resource (invoices) and scope (invoice date range) with the two required parameters named, so the agent knows exactly what it retrieves. It lacks explicit sibling differentiation — nothing distinguishes it from ecourier_get_invoice_fees or ecourier_list_payments — but the resource is unambiguous.

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?

Gives a hard operational constraint ('at most 31 days apart: e-Courier rejects anything else') and lists optional narrowing filters, which implies when the tool applies. It never states when to prefer this over related list/lookup siblings, so routing is left to inference.

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