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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so no side-effect warning is needed. The description adds useful computation details: it uses the current NBP reference rate and is exact to the grosz, and it states the returned values (days late, rate, interest).

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?

Three short sentences with no filler; the main purpose and output are front-loaded and the sibling routing is a single closing sentence. Every sentence earns its place.

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 covers the return values (days late, rate, interest), input scope, rate variants, and precision. There are no gaps that would prevent an agent from selecting and calling the tool correctly.

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 input schema already documents every parameter, including enum meanings and formats. The description adds context like the NBP reference rate and Polish statutory article, but it does not materially explain the parameters beyond what the schema provides, so the baseline 3 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 names a specific verb ('Calculates'), resource ('Polish late-payment interest'), and scope ('one or more overdue amounts'), and distinguishes itself from sibling create_interest_note by noting the formal note is a separate action. It is immediately clear what the tool does and how it differs from related tools.

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 explicitly says to use create_interest_note when the goal is to issue a formal interest note, providing the key routing decision. The opening phrase states the applicable condition: overdue amounts for which interest needs to be calculated.

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