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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is known. The description adds useful behavioral context: 'Local rendering' (no external calls) and the return format as base64. It does not contradict the annotations and provides additional operational detail beyond the structured metadata.

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 with no redundancy. The main action is front-loaded, and the extra detail (local rendering, pairing with send_email_resend) is concise and relevant. Every sentence earns its place.

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?

There is no output schema, but the description clearly states the return type (base64-encoded PDF). It also covers the local rendering aspect and suggests a companion tool. While it doesn't discuss error handling or edge cases, the annotations and schema cover validation and safety, making it sufficiently complete for an agent to call it correctly.

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 every parameter already has a clear description. The tool description adds no extra meaning beyond the schema, only restating that it uses supplier, customer, line items, and totals. The baseline of 3 is appropriate given the schema fully documents parameters.

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 states a specific verb ('Generate'), a concrete resource ('polished, human-readable PDF invoice'), and the input ('structured invoice data') and output ('base64-encoded document'). It clearly differentiates from the sibling format_peppol_invoice by emphasizing human-readable PDF, and the local rendering note adds specificity.

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 explicit guidance on when to use this tool versus alternatives. It mentions pairing with send_email_resend, but that is not a sibling tool and does not clarify selection criteria. No exclusions or conditions are provided for choosing this over format_peppol_invoice or other invoice-related tools.

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