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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds the return-content profile (line items, payments, amount due) and an auth requirement ('Cotlet API key with access to this app'), which are genuinely useful beyond the 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?

The content is front-loaded, but the first and second sentences redundantly restate 'line items, payments recorded and amount due'. That duplication costs space without adding information.

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 explaining the return contents, and it does (every line item, payments, amount due) plus auth needs. It is complete for a single-resource read tool, missing only explicit sibling routing.

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 coverage is 100% and the invoice_id description already points to list_invoices, so the schema does the heavy lifting. The description adds nothing about the parameter, so baseline 3 applies.

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 and resource ('Get invoice') and immediately names the returned content: 'line items, payments recorded and amount due'. This clearly separates it from sibling list_invoices and mutation siblings like send_invoice or record_payment.

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?

Gives a concrete use context: 'Use it to check an invoice before sending it or recording a payment'. This implies the when-to-use condition well, though it never names the alternative tools (e.g., list_invoices for enumeration) explicitly.

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