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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful behavioral detail: it renders an interactive dial, defaults to today, and accepts ISO dates. Minor gap: the phrase 'visually move things around' could imply persistence, but readOnlyHint clarifies that this is not a mutating operation, so no contradiction exists.

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 sentences, no filler. The primary purpose is front-loaded, usage guidance follows, and the alternative is cited at the end. Every clause earns its place.

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 visual renderer with readOnlyHint, the description is nearly complete. It covers purpose, usage, parameter, default, and alternative. The only small gap is not explicitly stating that interactive moves are not persisted, but this is implied by the readOnly annotation and the description's focus on 'SEE' rather than 'change.'

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?

Even though schema description coverage is 0%, the description fully explains the only parameter: 'Defaults to today; pass `date` (ISO YYYY-MM-DD) for another day.' It covers format, default, and semantics in one clause.

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 opens with a specific verb and resource: 'Render the user's day as the interactive 24-hour reassign dial.' It clearly distinguishes itself from get_schedule by contrasting visual rendering with text-based reading, so an agent can tell them apart without opening schemas.

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?

Explicitly states when to use: 'use it whenever they want to SEE their day, their schedule laid out, how full it looks, or to visually move things around.' It also names the alternative for text-based reasoning: 'For reading or reasoning about the plan in text, prefer get_schedule.' This is unambiguous routing.

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