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

Annotations already mark it read-only and idempotent, and the description adds non-obvious behavioral context: it returns bundled reference material, optionally filters or calculates based on inputs, does not fetch live data, and does not change accounts. It also explains a key timing nuance (the 30-day gap) that shapes what the agent can promise the user.

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 dense but not padded; the first sentence leads with the trigger cases and the key question. It is slightly long, with a compound final sentence, but every clause carries decision-relevant 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 one optional parameter, full schema coverage, rich annotations, and an output schema present, the description covers the main usage trigger, the Canadian-specific content, the non-live behavior, and the consequence for the user's file. Nothing essential is missing for an agent to invoke it 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?

The schema already documents daysPastDue with 100% coverage, and the description adds the practical effect: 'Changes which part of the answer leads.' This is meaningful extra semantics beyond the schema, though modest.

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?

Description opens with explicit use cases ('missed, late, or nearly-late payment', 'how long will this hurt me') and names the exact resource: what happens when a Canadian credit card payment is missed, including the 30-day gap, R1-R9 scale, and retention duration. This scope is specific enough to separate it from siblings like explain_retention_periods or explain_when_issuers_report.

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 says plainly when to use the tool and what it is not for ('does not fetch live data or change accounts'), which gives clear decision context. It does not explicitly name sibling tools as alternatives or state a when-not-to-use condition, so it stops short of a 5.

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