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

Annotations already carry readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: money is computed in integer cents to avoid float rounding errors, and it returns base64 PDF plus total. It stops short of stating size limits or failure modes, but it clears the lower post-annotation bar.

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?

Three tight sentences with the core purpose front-loaded, followed by the numeric-precision guarantee and the return shape. No padding or redundancy.

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?

An output schema is present so return values need not be detailed, and the description still states the base64+total shape. For a deeply nested single-object tool with 0% schema coverage it covers the salient fields, but leaves date formats, currency pattern, and the notes/number fields entirely to the schema, leaving minor gaps.

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 0%, yet the description compensates well by naming the major input groups: company and client details, line items with quantities and rates, tax rate, and optional percent-or-flat discount. This maps closely to the nested from/to, items, taxRate, and discount properties, though currency format, date fields, and notes are left to 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?

States a specific verb (Build) and resource (invoice or quote PDF) and enumerates the inputs it consumes (company/client details, line items, tax rate, discount). An agent can distinguish it from siblings like generate_resume or images_to_pdf without opening any schema.

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?

No when-to-use or when-not-to-use guidance is given, and no alternatives are named. The invoice-vs-quote choice is handled by the schema's kind enum rather than by the description, so the agent gets no routing help beyond what the structured field already provides.

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