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

Annotations already cover read-only, idempotent, closed-world, non-destructive behavior, so the bar is lower. The description adds genuine substance beyond them: the weekend-observance shift rule (Saturday to Friday, Sunday to Monday) and the statutory basis in 5 U.S.C. 6103, which clarify what the results mean.

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, front-loaded with the resource and scope, then the return contents, then the usage cue. The density is justified because no output schema exists to carry the field-level detail.

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 no output schema, the description fully enumerates the returned fields (name, actual date and weekday, observed date, governing rule), and annotations cover the safety profile. An agent has everything needed to call it correctly and interpret results.

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% and the single `year` parameter is fully documented in the schema with the same 2021-2100 range. The description repeats rather than extends that information, so the baseline of 3 applies.

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 (list U.S. federal holidays) with an exact scope: eleven holidays, one calendar year, 2021-2100. The scope and content detail clearly separate it from siblings like next_federal_holidays and check_business_day.

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?

"Use it to answer which days federal offices close in a year" gives a clear intended context for invocation. It stops short of naming alternatives or exclusions, so the agent must infer when next_federal_holidays would be preferable.

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