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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so safety is covered. The description still adds real context the annotations cannot: the covered universe (420 tickers), and critically that each date is either 'confirmed by the company or estimated from its payment rhythm' — a data-reliability caveat an agent must know before presenting dates as fact.

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?

Front-loaded with the resource and its output, then the caveat, then the filter hint — good ordering and no filler paragraphs. Minor noise: the awkward fragment 'of the 420 Portfolio Terminal covers' and the advisory 'Buy before the ex-date' sentence, which is orientation rather than tool description.

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?

An output schema exists, so return values need no explanation, and all five parameters are fully documented in the schema. The description supplies the remaining essentials: universe scope, date-estimation caveat, and the single-ticker filter path. Nothing an agent needs in order to call it correctly is missing.

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 mutual exclusivity of `month` and `from` and the range bounds, so the baseline of 3 applies. The description restates only that `symbol` filters to one ticker, adding no syntax, format, or behavioral nuance 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 first sentence names a specific verb+resource ('going ex-dividend'), the asset universe (US stocks and ETFs), the time dimension (a month or a date range) and the projected fields (ex-date, pay date, DPS, yield, frequency, confirmed vs estimated). That is far more specific than the name alone. It does not explicitly contrast itself with the adjacent `earnings_calendar` sibling, though the dividend framing makes confusion unlikely.

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?

Usage is only implied: 'Filter by one ticker with `symbol`' hints at the narrowing path, and 'Buy before the ex-date to receive the dividend' is a domain tip rather than invocation guidance. Nothing states when to choose a month vs. a from/days range, or when to reach for this over `earnings_calendar` or `analyze_ticker`.

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