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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the description does not need to re-establish safety. It adds useful operational context by naming the required OAuth scope 'invoices.read' and warning never to ask for a KSeF token or password, which helps prevent an agent from requesting inappropriate credentials.

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 tight sentences. The core purpose, scoping condition, and parameter default are front-loaded, and the second sentence adds only the essential authentication/security constraint.

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 low-complexity read-only listing tool with one optional parameter, an output schema, and clear annotations, the description covers what the tool returns, the default and cap for withinDays, required OAuth scope, and credential safety. Nothing essential for correct invocation 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?

Schema description coverage is 0%, so the description carries the burden for the single parameter. It explains that withinDays controls the due window, provides the default of 7, and states the maximum of 90, adding meaning beyond the schema's bare minimum and maximum constraints.

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: 'List unpaid cost invoices on the linked KSeF Płatności account.' It adds precise scoping conditions, 'overdue or due within withinDays', so the agent can distinguish this filtered view from the broader sibling tool list_cost_invoices without opening either schema.

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 description gives clear context for when this tool applies: unpaid invoices that are overdue or fall within a configurable day window. It does not explicitly name alternatives such as list_cost_invoices or state when not to use this tool, so it stops short of fully explicit routing guidance.

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