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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so safety is covered. The description adds genuinely non-obvious behavior: the response shape (hub URL plus dates) and, critically, the fallback to a seasonal mode when no moment is active — an agent would otherwise not know a null-ish result still carries meaning.

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, front-loaded with the outcome and followed by examples and the fallback case. Every clause carries information; nothing is padding.

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 zero required parameters, rich annotations, and an output schema, the description covers everything needed to invoke it correctly. Only minor ambient details (what 'now' is anchored to, caching/freshness) are absent, and those are arguably outside its remit.

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?

One optional parameter with 100% schema description coverage and an enum, so the schema fully documents locale. The description adds nothing about it (e.g., default locale), which is acceptable at this coverage level but no better than baseline.

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 ('Returns') and a precisely scoped resource: the seasonal/cultural moment currently running in Paris. The concrete examples (Fashion Week, Christmas, heatwave) plus the fallback case ('seasonal mode when none is running') make it unmistakably distinct from siblings like search_events or get_event, which operate on explicit entities rather than ambient city state.

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?

The word 'currently' implies the usage context (real-time, no arguments needed), but the description never states when to prefer this over get_event or search_events, nor any exclusion. Usage is inferable rather than stated.

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