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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds useful non-obvious behavior: a hard cap of 200 events with a `truncated` flag, all filters judged in the viewer's zone, and the fact that events without start times never match a tod filter.

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?

Scope and key behaviors are front-loaded in the first sentence, and the second sentence enumerates filters compactly. The final clause contrasting with GET /api/events is a bit long-winded but still earns its place by preventing a misuse.

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?

There is no output schema, yet the description discloses the truncation signal and grouping, plus read-only annotations. For a 6-param, zero-required read tool this is largely complete, though return-shape details (fields per event) remain unstated.

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%, so the schema already documents tz defaults, tod boundaries, day values, free, lang and craft. The description adds a little rationale (tod/day are computed per event from its own zone, hence living here) but largely restates schema content, so the baseline 3 stands.

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 states a specific verb and resource ('Online events, by day in the viewer's time zone') and scopes it precisely: published online/hybrid events, next 30 days, grouped by the viewer's start date. It differentiates itself from GET /api/events (online=1), which is a strong distinction, though it names an HTTP endpoint rather than the sibling MCP tools like list_events.

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 tells the agent when this tool applies versus the alternative (GET /api/events with online=1) and explains why tod/day filtering lives here. It gives clear usage context but does not name or rule out sibling MCP tools such as list_online_event_picks or count_events_by_craft.

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