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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds that the result includes reminder recommendations ('what to send the client now and next') following a 'proven reminder schedule' — useful output-shape context that annotations don't carry. However, the schedule itself is never characterized, so the added context stays vague.

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?

A single front-loaded sentence that leads with the primary computation. It is slightly overloaded by the trailing 'following a proven reminder schedule' clause, which reads as promotional rather than informative, but nothing is redundant enough to cut wholesale.

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 only two simple parameters and no output schema, the description needs to convey the return shape, and it partly does (day count plus current/next reminder suggestion). It leaves the actual structure of the reminder recommendation and the schedule stages unexplained, which is a meaningful gap for an agent that must decide how to use the result.

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 100%, including the note that `today` defaults to New York time, so the schema does the heavy lifting. The description's parenthetical '(or until it is due)' clarifies that past and future due dates are both handled, but it adds no format or interpretation detail beyond what the schema already states.

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 concrete computation ('how many days late an invoice is (or until it is due)') plus a second output ('what to send the client now and next'). That is specific enough for an agent to know what it gets back. It stops short of distinguishing itself from the sibling payment_reminder_email, which appears to overlap on the 'what to send' half.

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?

There is no explicit when-to-use guidance, no prerequisites, and no exclusions. With three siblings (invoice_due_date, late_fee_calculator, payment_reminder_email) plausibly applicable to the same task, the description never says which situation selects this tool over them.

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