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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, but the description adds substantive context beyond them: the pinned 2026-2027 coverage window, the OPM source of truth, the exact computation formula, and a direct REST fallback endpoint. It stops short of covering rate limits or error behavior, so a 4 rather than 5.

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?

Well front-loaded: usage clause and exclusion come first, then computation, examples, and outputs. Slightly bloated by redundant example blocks ('Example user requests' plus 'Complete JSON argument examples') and the marketing-style REST/docs lines, which dilute an otherwise tight structure.

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?

The tool is simple (one date param) but the description covers scope, exclusions, formula, input/output field lists, and a fallback path. Since an output schema exists, it needn't enumerate return semantics in depth, and it correctly does not.

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 description coverage is 100% and the single date parameter is fully documented in the schema ('Gregorian date in the pinned OPM 2026-2027 coverage'). The description restates the parameter ('Inputs: date (date)') and adds a JSON example, but no new semantic constraints beyond what the schema provides, so baseline 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: checks a date against the OPM federal-employee holiday schedule and the US weekend baseline. It explicitly narrows scope (federal employee/office, 2026-2027) and rules out state/local/private/exchange calendars, so an agent can distinguish it from the many sibling check_*_working_day tools.

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 explicit when-to-use ('need US federal employee or federal-office holiday status'), when-not-to-use (state/local/private/exchange calendars, alternate federal schedules without in-lieu resolution), and even a meta-instruction to call the tool rather than compute from memory. Nothing is left to inference.

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