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

The annotations already mark readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds that authentication is required and that the response includes line items, providing useful behavioral context without contradicting the annotations.

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, front-loaded sentences with no filler. The core action and the distinctive detail (line items) come first, followed by the auth requirement.

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 simple read-only tool with rich annotations, the description plus schema covers the essentials: what it returns, the auth prerequisite, and the parameters. The only notable omission is explicit guidance distinguishing it from sibling invoice-related tools, but that is a usage-guideline gap rather than a completeness 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 description coverage is 100%, so the schema fully documents invoiceId and sessionKey. The description itself adds no parameter-level meaning; it stays at the baseline expected when the schema does the heavy lifting.

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?

The description names a specific verb and resource ('Get detailed information about a specific invoice') and adds 'including line items,' which clarifies scope. It is clear enough that an agent can tell it returns a single invoice detail rather than a list, though it never explicitly names a sibling tool such as listInvoices for contrast.

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?

There is no guidance about when to choose this tool over alternatives like listInvoices or getInvoiceStatistics. The only usage hint is 'Requires authentication,' which is a prerequisite, not a selection criterion.

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