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

No annotations exist, so the description carries the full disclosure burden. It usefully reveals a constraint absent from the schema (year is limited to 2026 or 2027) and the conditional content of results (national only vs. plus municipal/regional). It omits return format, ordering, and error behavior for invalid years.

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?

A single sentence that front-loads the verb and resource, then layers the year constraint and the conditional scope of results. No filler, no restatement of the name or title.

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 two-parameter read tool with no annotations and no output schema, the description covers purpose, the year value range, and conditional output content. It leaves the return shape and the relationship to next_holiday unexplained, which is a real gap given there is no output schema to fall back on.

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 only 50%, with 'year' carrying no schema description; the description fills that gap by pinning year to 2026 or 2027. Municipality semantics live almost entirely in the schema field description, so the description adds marginal value there but adequately compensates for the undocumented required parameter.

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 with scope: 'List Portugal's public holidays for a year'. It contrasts implicitly with the sibling next_holiday via the plural 'holidays for a year' framing, but never names the sibling or explicitly rules it out, so it falls short of a 5.

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?

Usage is implied through the '(2026 or 2027)' constraint and the conditional 'when a municipality is given', which tells the agent how to broaden the result set. However, there is no explicit guidance on when to pick this over next_holiday or what happens outside the supported year range.

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