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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is fully covered by structured data. The description adds the useful detail that two URL kinds are returned (preview and original), but says nothing about what happens when no document exists yet, or whether URLs are signed/expiring. With no output schema this is a modest but real contribution.

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 short sentence that front-loads the verb and resource with zero filler. Nothing is redundant or buried.

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?

The tool is simple (one fully-documented param, clear read-only annotations), so little is required. Still, with no output schema the description should more fully characterize the return value — e.g. the shape of the link object, when values are absent, or URL expiry — and should distinguish this from preview-invoice, which it does not.

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?

There is a single parameter and schema description coverage is 100% ('Invoice ID' with a numeric pattern), so the schema already fully documents the input. The description adds no syntax, format, or source guidance beyond that, which is the expected baseline for a one-param tool with full coverage.

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 (get) and a well-defined resource (invoice document links: preview and original URLs), which is more specific than a bare 'get invoice'. However, it does not differentiate itself from close siblings like preview-invoice, generate-invoice-pdf, or get-document, so there is some residual ambiguity about which retrieval tool to pick.

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 description gives no when-to-use guidance, no preconditions (e.g. that the invoice must already have a generated document), and no mention of alternatives such as preview-invoice or generate-invoice-pdf. The agent must infer the routing from the name alone.

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