On this day in history

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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description's job is to add context, which it does: it discloses that results are fixed to the current day and that `date` is rendered inconsistently (Gregorian with year for history, Jalali day for national occasions). That format caveat is exactly the kind of thing an agent cannot learn from annotations, though pagination/result size remain unmentioned.

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 short sentences, front-loaded with the resource and scope, with no wasted phrasing. The inline code formatting for `date` is slightly fussy but harmless.

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 read-only, single-optional-parameter tool with an open-world external source and no output schema, the description covers scope, content types, and the data-format quirk well. It falls short only on not describing the item shape beyond the `date` field or result volume.

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% with one optional enum-ish `kind` parameter, so the schema already carries the semantics and baseline 3 applies. The description names the three categories (events, birthdays, deaths) that map to the enum values but adds no syntax or default behavior beyond that.

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 (List) and resource (today's historical events, birthdays and deaths of notable people), plus the source behavior it mirrors (Time.ir's 'today' page). The 'Today only' constraint plus the date-format note makes it distinguishable from ti_events and ti_search_events even though no sibling is named.

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 'Today only' scope implicitly tells the agent this is not an arbitrary date-range query, so an agent can infer that ti_events/ti_search_events are needed for other dates. However, no sibling is named and there are no explicit when-not-to-use statements, leaving routing to inference.

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