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

Annotations already provide readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false, which establish safe read-only behavior. The description adds the endpoint URL, the open/curated data source (Wikipedia), and the no-auth requirement, giving useful context beyond the annotations. It does not cover pagination or output structure, but an output schema exists and the annotations carry the safety profile.

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 three sentences with no filler. The first sentence immediately states what the tool returns and the selection criteria; the second explains the primary parameters; the third identifies the underlying API and auth status. Every sentence adds value and the most important information is front-loaded.

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 date-and-category-filtered read tool, the description covers the endpoint, the categories, language handling, and auth requirements. An output schema exists, so return-value documentation is not required from the description. It is almost complete; the only minor gap is that it does not spell out the 2-digit zero-padded format for month and day, though the input schema already enforces it with patterns.

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 all four parameters are documented in the schema. The description adds guidance on how to combine 'type' (category selection) and 'lang' (language edition, default en) with the date parameters, which connects the parameters to the API's semantics. It stops short of detailing edge cases like invalid month/day combinations or the exact format expected for 'month' and 'day', but the schema patterns already cover format.

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 clearly identifies the resource ('historical events, births, deaths, holidays, or editor-selected highlights'), the temporal filter ('given month/day'), and the API source ('wikipedia.org/api/rest_v1/feed/onthisday'). It distinguishes the tool from siblings like wikipedia.feed.featured and wikimedia-rest.pages.summary by naming the specific content categories and date-based selection.

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 explains how to select the category with 'type' and the language edition with 'lang', and it names the default (en). It also identifies the source and notes no auth is required. However, it doesn't explicitly state when not to use this tool or point to a sibling alternative, such as wikipedia.feed.featured for today's featured content or search endpoints for non-date-based queries.

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