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

With readOnlyHint=true already in annotations, the description adds value by detailing what the returned document includes (totals, status, line items, contact, money direction) and clarifying the range of accepted ids across document types. This goes beyond the annotation and helps set expectations for the response content.

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 wasted words. The core action and returned fields are front-loaded in the first sentence, and the second sentence clarifies the input scope efficiently.

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 simple single-parameter read tool with no output schema, the description discloses the key return fields and the full range of acceptable ids. It does not mention error cases or auth, but these are not critical for correct invocation given the read-only annotation and simple input.

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?

The schema only describes the id as 'Document id', while the description adds meaningful semantics: it accepts any business-owned document id, including invoice, quote, and credit-note ids from list_documents and list_invoices. This is useful guidance beyond the 100% schema coverage.

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 and resource ('Get one document by id'), lists the returned fields (totals, status, line items, contact, money direction), and distinguishes itself from list_documents/list_invoices by clarifying it accepts the ids those tools return.

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 gives clear context on the accepted scope ('any document id this business owns') and points to list_documents and list_invoices as sources of valid ids, which implicitly signals when to use this tool. However, it does not explicitly state when to prefer alternatives over get_document, such as using list_documents for bulk retrieval.

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