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

Annotations already mark this as read-only, idempotent, and non-destructive. The description adds valuable behavior beyond that: refusal when nothing is overdue, no interest stated, a one-hour .txt download link, and the Pro requirement for level 3. There is no contradiction with the readOnlyHint since this produces generated content rather than mutating persistent state.

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 compact and front-loaded with the core purpose every-OVERDUE-invoice and level options. Every sentence adds useful information: refusal condition, content scope, link expiry, and Pro gating. No filler.

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 tool with six parameters, full schema coverage, and no output schema, this description covers the key runtime behaviors an agent needs: output is a downloadable .txt link, it fails if nothing is overdue, content includes invoices and totals, and level 3 has a license requirement. The remaining gaps are covered by the input schema.

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%, so the schema already documents all six parameters. The description reinforces the level meanings and adds the Pro constraint, but it does not substantially enrich parameter semantics beyond the schema.

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 ('Write a payment chaser') and resource ('dunning letter') with clear level semantics. It distinguishes itself from sibling statement tools by focusing on overdue invoices and payment chasing.

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 clearly indicates when the tool applies: whenever overdue invoices exist, with level selection. It also gives an explicit exclusion ('Refused if nothing is overdue'), although it does not name sibling tools as alternatives.

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