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

Annotations already declare readOnlyHint, idempotentHint, and a non-destructive operation, so safety is covered. The description adds a useful pairing/identification constraint and warns against title/date lookup, but it does not disclose not-found behavior or any provider-specific response details. This is moderate added value beyond 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 with the core action and required IDs front-loaded, followed by a critical guardrail. There is no filler, repetition, or unnecessary detail.

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 read-only get-by-ID tool, the description plus the fully documented input schema and safety annotations give an agent everything needed to invoke it correctly. The return value is evident from the name and operation type, and no side effects need disclosure. Not-found behavior would be a nice addition but is not essential for correct invocation.

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%, and each parameter description already documents exact ID sources, pairing, and the rule to never pass titles or dates. The tool description's mention of exact parent calendar_id and event_id restates the schema relationship without adding new semantics. 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 states a specific verb ('Get'), the resource ('one event'), and the required identifying pair (exact parent calendar_id and event_id). This clearly distinguishes the tool from siblings like calendar_list_events and calendar_get_calendar. The negative instruction about not using title or date sharpens the purpose even further.

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 description gives a clear when-to-use condition: call this only when both exact calendar_id and event_id are available. It also gives an explicit when-not: never identify an event only by title or date. It does not name sibling tools or point to calendar_list_events/calendar_create_event as ID sources, though that information appears in the schema.

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