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

Beyond the readOnlyHint annotation, it discloses non-obvious behavior: every call creates a duplicate file, the artifact is retained rather than imported into the books, and a missing or cross-business id fails with reason document-not-found. It also states what the call returns (the new file's id and name), which annotations do not cover.

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?

Purpose is front-loaded in the first clause, followed by return handling, duplication warning, retention semantics, and error behavior in that order. Every sentence carries a distinct, actionable fact with 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?

With no output schema and a single-parameter input, the description carries the remaining burden and does so: it names the returned fields, explains how to surface the file to the user, warns about duplicate artifacts, and specifies the failure mode. Nothing needed to invoke it correctly is missing.

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?

There is only one parameter and the schema coverage is 100%, with the schema already naming the accepted document sources (list_invoices, get_document). The description restates that the id can be an invoice, quote, credit note or other document and adds the cross-business rejection rule, but adds little beyond the schema. A 3 baseline is appropriate.

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 gives a specific verb and resource (save a document as a PDF in the business's Files) and scopes what counts as a document (invoice, quote, credit note or any other kind), plus the rendering rule 'drawn as the customer sees it'. This clearly separates it from siblings like list_files, attach_file, remove_file, and save_document.

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?

It states the operating condition ('each call saves a new copy, so call it once per request') and tells the agent what to do with the result (cite it as a file tag so the user can open and download it). It lacks an explicit comparison to alternatives such as list_files or send_document, so the agent must infer when another sibling is the better choice.

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