on_this_day

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

With no annotations, the description carries the full burden and does reasonably well: it discloses the data source, timezone basis (UTC), and the key behavioral quirk that results are a 'random sample' rather than a deterministic or complete list. It does not cover auth needs or rate limits, but for a public read-only feed tool that gap is minor.

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 tight sentences: the retrieval action and source come first, the return shape second, with no redundant restatement of the tool name. Every clause carries information.

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 exists, so the description must describe returns — and it does ('year + description + Wikipedia link', random sample). Combined with a fully documented 2-param schema, an agent has everything needed to invoke it correctly.

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% (both lang and count are documented with defaults and max), so the baseline is 3. The description adds the UTC date framing but nothing further about lang semantics or count behavior 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?

States a specific verb+resource ('Get historical events ... from Wikipedia's On This Day feed') and scopes it to today's date in UTC. It also names the sibling it pairs with (featured_article), making it distinguishable from random, did_you_know, and deaths_on_this_day.

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 phrase 'great daily content hook alongside featured_article' gives an implied usage context, but there is no explicit when/when-not guidance and no mention of closer alternatives like deaths_on_this_day (which covers the same date concept) or random. Usage must be largely inferred.

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