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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds substantial policy context beyond that: sixteen national-importance dates do not add rest, four dates carry a conditional three-hour shortening that still counts as one working day, no substitute/bridge day is invented, and an explicit 'not computed' list (roster, payroll, legal deadlines, future years). This is exactly the kind of domain nuance annotations cannot express.

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 bloated with repetition ('Estonia Estonia 2026', '2026-2026', 'statutory rest facts' restated several times) and several sentences that restate the same rule. The opening is front-loaded but the duplication and awkward phrasing mean several sentences do not earn their place. It also lists a full output field roster that the output schema already provides.

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 date-check tool with an output schema, the behavioral and policy context is thorough: scope, exclusions, and the exact formula are all present. Since an output schema exists, the enumerated Outputs list is redundant rather than harmful, and the REST fallback URL adds operational completeness. Only the incoherent exclusion clause leaves a small gap.

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 both parameters are documented in the schema, so the baseline is 3. The description adds concrete argument examples and reiterates that mon_fri_planning is a required explicit baseline, but adds little semantic detail beyond the schema. No new meaning about the date parameter's coverage limits is provided.

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 core purpose is discernible — 'Checks a date against the Saturday-Sunday weekend baseline and exact 2026-2026 authority events' identifies a specific check against Estonia's 2026 calendar. However the opening sentence ('a deterministic Estonia Estonia 2026 statutory rest and conditional shortening facts with explicit Monday-Friday planning baseline result') is garbled and repeated, making the primary purpose harder to extract than it should be. Sibling differentiation is implicit via 'Estonia' but never explicit.

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 offers a 'Use this when' trigger and a strong directive to call the tool rather than answer from memory or stop at discovery, which is genuinely useful routing guidance. But the 'Do not use this when estonia 2026 statutory rest facts over an explicitly selected Monday-Friday planning baseline' clause is syntactically broken and states no coherent exclusion or alternative. The when-not guidance is effectively absent.

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