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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds that generation preserves prefix and zero padding, but says nothing about determinism, duplicate risk, or the count limit beyond what the schema states.

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 with the core purpose front-loaded. It is long but every clause carries content, so nothing obvious should be cut.

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 7 optional parameters, no output schema and no required fields, the definition is adequate but not complete: it never states what the returned value looks like (a single string vs. a list for count>1) or confirms the output format. For a read-only generator this is a modest gap rather than a fatal one.

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 71%, so most parameters are documented. The description adds genuine value by mapping parameters to modes (lastNumber for next-after; prefix/separator/datePart/digits for a run) and explaining the zero-padding behavior, going beyond the schema's field-by-field listing.

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+resource ('Generate invoice numbers') and enumerates the two operational modes: next-after a given number, or a run in a chosen format. This is clearly distinct from invoice-writing siblings like create_invoice/list_invoices, though it never names them explicitly.

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 two modes and the parameters that select each one are spelled out ('next number after a given one...' vs. 'a run of numbers in a chosen format'), giving clear implied context for choosing parameters. No when-not guidance or explicit alternatives are given, so it falls short of a 5.

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