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

Beyond the annotations (readOnlyHint, idempotentHint, destructiveHint), the description adds critical behavioral context: it states that no account access or storage occurs, that the link contains invoice data and must be shared only with the intended recipient, and that human review is required. These disclosures go well beyond what annotations provide, enhancing safety and privacy awareness.

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?

The description is two sentences, front-loaded with the core purpose and return values, then adding constraints. Every sentence adds value: the first states what it does and returns; the second gives usage instructions, behavioral boundaries, and a privacy caution. It is concise, well-structured, and avoids 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?

Given the tool's complexity (40 parameters, nested objects, no output schema), the description covers the essential context: it explains the tool's purpose, what it returns, how to handle missing information, and privacy/security considerations. It does not enumerate all parameters or return details, but the schema provides the structure. The description is adequate for an agent to understand when and how to use the tool, though it could be more explicit about specific field requirements.

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?

With schema description coverage at only 13%, the description should compensate by explaining the meaning of key parameters. It does mention 'explicit VAT treatment' (relating to the 'tax' param) and warns against inventing payments/terms, but it does not clarify the majority of the 40 parameters, including nested objects like seller, customer, extras, and payments. The description offers only high-level guidance without detailing parameter semantics.

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 clearly states a specific action: preparing a UK vehicle sales invoice draft from user-supplied facts, and explicitly mentions the return of calculated totals and a private review link. It distinguishes the draft nature from final issuance and gives a concrete resource, making the purpose unambiguous.

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 instructs the agent to ask for all required fields and explicit VAT treatment, and warns against inventing facts, payments, or terms. It also notes that human review and download are required before issuing, providing clear context for when this tool is appropriate. There are no sibling tools to differentiate from, but the guidance is actionable.

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