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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered, but the description adds real behavioral context: a draft has no number until finalised, and it lists the exact data returned including reminders already sent. The auth note about the Cotlet API key is a useful prerequisite not present in structured fields.

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?

Front-loaded and appropriately short, leading with the resource and following with return contents and the draft/number caveat. Minor redundancy: 'reminders already sent' appears in both the first and second sentences.

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, the description carries the burden of describing return values and does so well (customer, dates, line items, net/tax/gross, status, open amount, reminders), plus the draft versus finalised number distinction. Adequate for a simple single-entity read tool, though it says nothing about not-found or permission-failure behavior.

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?

Only one parameter and schema description coverage is 100%, so the schema already documents document_id and its source (list_documents or create_invoice). The description adds no parameter syntax or format details beyond that baseline.

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?

States a specific verb (get) and resource (one document) and clarifies the scope as a single invoice or quote with its lines, totals, status and reminders. It is distinguishable from list_documents and download_document_pdf, though it does not explicitly name those siblings to route the agent.

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?

Usage is implied rather than stated: 'One document' combined with the schema note that the ID comes from list_documents or create_invoice tells the agent this is a single-record fetch. There is no explicit when-to-use/when-not or alternative routing guidance.

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