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

Annotations only declare the mutability profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false, openWorldHint=false). The description adds genuinely new behavioral facts: the output is a download link that expires after one hour, the page format is A4, and the document embeds the reversed invoice. The trailing 'Pro' hints at a plan/entitlement gate, though it is unexplained and never states what happens if the account is not entitled.

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?

It is a single front-loaded sentence that puts the action and artifact first, then appends the return-value and layout details after the colon. Slightly run-on and the dangling 'Pro' token is unexplained, but there is no filler.

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?

For a two-parameter render tool with full schema coverage and no output schema, the description covers the action, the document content, and the shape of the return value (a one-hour download link), which is the critical missing piece an output schema would otherwise supply. It stops short of covering failure modes (invalid id, plan not entitled, expired link) which would round it out.

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%, covering both 'id' and 'out_path', so the schema already carries the parameter meaning. The description reinforces the download-link/one-hour lifetime for the out_path result but adds no syntax, format, or defaulting detail beyond what the schema says. Baseline 3 applies when the schema does the heavy lifting.

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 a specific verb ('render'), a specific resource ('one credit note'), and states the output artifact ('A4 print-ready document' plus 'download link'). It also scopes the content ('the invoice layout titled CREDIT NOTE, with the invoice it reverses'), which distinguishes it from credit_note_text and from purchase_order_pdf without needing the sibling schemas.

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 opening 'Call this tool to render one credit note' gives an implied when-to-use, and the 'download link valid for one hour' implies the transient nature of the result. However, it never names the alternative (credit_note_text) or states when-not to use this tool, leaving the agent to infer that credit_note_text is the non-PDF path.

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