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

Annotations already declare readOnlyHint=true and idempotentHint=true, and the description adds value by enumerating excluded data (recipient identity, payment data, generated values, free-form content, rendered HTML/CSS) and the opt-in requirement for line items. This goes beyond the annotation safety profile, though it does not describe the output structure.

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 sentences, front-loaded with the purpose and followed by concise exclusion details. No filler or redundant wording.

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?

Given the output schema and annotations, the description covers core behavior and exclusions. It leaves the exact meaning of 'semantic template projection' slightly vague, but the included exclusions and opt-in rule are sufficient for safe invocation.

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 each parameter already has a clear description. The description's mention that 'line items require explicit opt-in' restates the includeLineItems default/false semantics without adding new meaning beyond the schema.

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 uses the specific verb 'Preview' and names the resource 'safe semantic template projection from an immutable invoice revision.' It lists exclusions, which distinguishes it from sibling get_invoice_template that would return the full template.

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 word 'Preview' and 'safe' imply it is meant for non-destructive inspection before acting, but the description never names an alternative tool or states when not to use it. Usage must be inferred from context.

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