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

With no annotations, the description carries the full burden and does the most important thing: it disproves the obvious assumption that this tool sends the letter ('Nothing is emailed or sent anywhere... sending it is your act'). It also hints at ladder state advancement. It does not cover error behavior or whether re-issuing a sent letter has side effects.

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?

Two sentences and every clause earns its place, with the core action front-loaded. The dense em-dash parenthetical in the first sentence slightly hurts scanability, but nothing is redundant.

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?

No output schema, and the description covers what an agent needs: what is produced (letter text in Markdown or printable HTML), that nothing is transmitted, how to act on it (letter_sent), plus stage/date/format semantics. Nothing material is missing for a rendering tool.

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%, so a 3 is the baseline, but the description adds real meaning: it explains what each stage value produces ('reminder 1 polite, reminder 2 firm with the late fees note, final notice before-action wording') and that html is 'self-contained printable,' which the enum labels alone do not convey.

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?

States a specific verb and resource ('generate the letter for the current stage of the ladder') and enumerates the three stage variants, so an agent can distinguish it from letter_sent, chase_today, and aging_summary without opening any 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?

Gives the triggering condition (chasing an unpaid invoice at the currently-due stage), an override condition for the stage param ('to preview or to re-issue a letter already sent'), and routes the follow-up action explicitly: 'Record the sending with letter_sent so the ladder advances.'

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