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

readOnlyHint=true already covers the safety profile, so the bar is lower, yet the description adds a genuinely useful behavioral fact: recurring series are expanded into per-occurrence events. That materially affects how an agent interprets the result set (expanded occurrences rather than series masters) and is not present in the annotations.

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 short sentences, zero filler. The core action and scope lead, and the recurring-expansion caveat follows as the one non-obvious detail worth including.

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 simple read-only list tool with full schema coverage and an existing readOnlyHint, the description covers the essentials plus the recurrence-expansion behavior. With no output schema it could say a bit more about what a returned event looks like, but nothing critical to correct invocation 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%, so start, end, accountId, and providerCalendarId are all documented in the schema, including their ISO 8601 formats and defaults. The description only echoes the time-range and single-calendar concepts, adding no format or default detail beyond the schema; baseline 3 is appropriate.

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 gives a specific verb ('List'), resource ('events'), and scope ('from a single calendar in a time range'), which clearly separates it from get_event (single event) and list_calendars (calendars, not events). It stops short of explicitly naming any sibling, so it is clear but not sibling-differentiating by name.

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 scoping phrase 'from a single calendar in a time range' implies when this tool applies, but there is no explicit guidance on when to prefer it over get_event, list_available_calendars, or find_free_time, and no stated prerequisites. 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.