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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false. The description adds useful behavioral context beyond those flags: what is included in the compact day and that clients with app display expose the day interactively. The UI interaction note refers to client-side user actions rather than the tool mutating data, so it does not contradict readOnlyHint.

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 front-loaded with the core purpose and content, followed by usage guidance and the date default. It is information-dense but not bloated; the first sentence is long, though every clause carries useful context.

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 one-parameter, read-only display tool with no output schema, the description gives enough detail about what the day view contains and when to use it. It could be slightly more explicit about return/output structure or differences from closely related siblings, but it is essentially complete for invocation.

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 the date format is already documented in the schema. The description adds meaningful default semantics not present there: omitting date means the user's today.

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: 'Shows one day to the user', and lists exactly what the day view contains. It names get_day_brief as producing the same compact day, but does not clearly distinguish when to choose show_day over that sibling or get_today.

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 a clear usage context: 'Fits when the user asks to see or plan their day or what is on it.' It also explains the optional date default with 'Omit date for the user's today.' It lacks explicit exclusions or alternative-tool guidance, so not a 5.

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