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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered elsewhere. The description's real contribution is disclosing that the result is a union of three sources whose membership changes with the supplied parameters, which is genuinely useful context. It says nothing about ordering, pagination, or result size, so a 3 is appropriate.

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 dense sentence that front-loads the default behavior (built-in public lists) before the two conditional extensions. Every clause carries information; the only minor cost is the slightly list-like 'plus ... and ...' cadence, which is still readable.

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 zero-required-parameter read-only listing tool with full schema coverage and no output schema, the description covers the sources and the parameter effects adequately. The one gap is whether both parameters may be supplied simultaneously and whether the result is deduplicated, but nothing critical to invoking it correctly is missing.

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 two property descriptions already state 'to include its custom lists' and 'to include the lists attached to it'. The description restates this meaning at the tool level, adding the framing that these are additive inclusions rather than filters, but contributes no format or edge-case detail beyond the schema. Baseline 3 for high coverage.

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 a specific verb-resource pair ('holiday lists') and enumerates exactly what set is returned: built-in public lists, workspace custom lists, and roadmap-attached lists. The parenthetical 'by key, e.g. US' clarifies the identifier form, which helps distinguish it from the singular get_holiday_list. It stops short of explicitly naming a sibling tool to contrast against, so it lands at 4 rather than 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 conditional phrasing 'when workspaceId is given' and 'when roadmapId is given', which tells the agent how to widen the result set. There is no explicit guidance on when to prefer this over get_holiday_list or get_holidays, nor any statement about whether the two parameters can be combined.

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