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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds the default calendar and coverage ranges, which is useful context but not a behavioral trait like auth requirements or error handling beyond what annotations supply.

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 field list, but then spends several sentences enumerating coverage dates for individual calendars, which is redundant given that an output schema exists. It is not bloated with fluff, but it is longer than necessary for a no-parameter list tool.

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?

With an output schema present, the description need not explain return values, and annotations cover the safety profile. It provides the key operational facts: what calendars exist and which is the default, making it complete enough for an agent to call this read-only tool 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?

The tool has zero parameters, so per the rubric the baseline is 4. The description lists output fields rather than input parameters, and the empty schema leaves no parameter semantics to clarify.

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 names the resource ('Shipped calendars') and enumerates the fields returned (id, name, source URL, rules, coverage, last verified, changelog), making it clear this tool lists calendar definitions. It distinguishes itself from holiday-listing siblings by focusing on calendar metadata rather than holiday dates, though it never explicitly names an alternative.

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 only usage hint is 'us-federal-opm is the default,' which implies a fallback when no calendar is specified, but there is no explicit when-to-use guidance, no mention of when not to use it, and no named alternatives such as list_holidays.

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