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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds meaningful context beyond them: no permission is needed, and the returned timezone governs interpretation of naive ISO date parameters on write tools.

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 short, front-loaded with the core return values, and then adds the critical usage rule and timezone interpretation note. Every sentence adds useful information without repetition.

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 zero-parameter read-only utility with a clear output schema and read-only annotations, the description is complete. It covers purpose, when to call it, permission behavior, and the downstream timezone semantics that matter for other tools.

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?

The tool has zero input parameters, so there is nothing to document in the schema. The description appropriately focuses on output meaning and timezone semantics rather than inventing parameter guidance.

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 states the tool returns the current local date, time, timezone, UTC offset, and weekday. This is an unambiguous resource and purpose, and it is readily distinguishable from unrelated siblings such as now_playing.

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?

It gives an explicit usage rule: call this FIRST to ground relative dates and never guess from memory. It also explains that date parameters on write tools are interpreted in this timezone, which tells the agent exactly when this tool is required.

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