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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds nothing beyond them: it never explains what counts as a "mirrored" event, whether it reads across accounts (relevant given accountId/providerCalendarId inputs), or what the scan returns.

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 front-loaded sentence with no filler, which is structurally clean. The problem is under-specification rather than verbosity: the one sentence leaves the core concept and scope unexplained.

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?

No output schema exists, yet the description never describes what the scan produces or how results are surfaced. For a cross-calendar comparison tool that requires 2+ calendars, the omission of both input constraints and return shape leaves the agent under-informed.

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 0% for the single `calendars` parameter, so the description carries the full burden and largely fails. It says "calendars" but never mentions the 2-20 item bounds, the required accountId/providerCalendarId pair, or that multiple calendars must be compared against each other.

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 verb ("Check") and resource ("calendars", "events"), so the basic action is recoverable. However, the defining concept "events that appear to mirror each other" is unexplained jargon, and nothing distinguishes this scan from siblings like list_events, get_event, or find_free_time.

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?

There is no statement of when to use this tool, no prerequisites, and no mention of alternatives such as list_events or find_free_time. The agent must infer the use case entirely from the tool name.

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