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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely new behavioral context: the default country scope, the fact that worldwide tier-1 days are included by default, and that countries=null means worldwide. Rate limits and pagination are not mentioned, but the tool appears to return a bounded list.

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 use case, then the return shape and scoping. The field enumeration in the middle is dense but each element earns its place since there is no output schema to carry it.

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 compensates by enumerating the returned fields (name, date, end_date, days, countries, kind, tier), their value meanings, and the default scoping logic. Combined with the fully documented schema, an agent has everything needed to call and interpret it.

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%, so all three parameters are already documented with defaults. The description restates the country override and clarifies that tier 1 means biggest, but adds little semantic detail beyond the schema (e.g. no guidance on how days interacts with multi-day events' end_date). 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 the resource precisely (festivals, holidays, shopping days, awareness days coming up) with concrete examples and the planning use case, which cleanly separates it from every sibling (scheduling, analytics, media tools). An agent can tell at a glance this is a read-only occasions lookup.

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?

Explains the default scoping behavior (user's calendar countries plus the biggest days everywhere) and how to override it with country or include_worldwide, which is clear usage context. It stops short of explicit when-not guidance or naming an alternative, though no sibling offers a comparable function.

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