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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true) by disclosing server-side quirks: events are force-set PRIVATE and unshareable regardless of input, isTrainingEvent is auto-set when isPrimaryEvent is, unknown eventType returns a 500, and blank name/date triggers a specific validation error. This is exactly the kind of hidden behavior an agent needs before invoking.

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?

Front-loaded with purpose and the key PRIVATE constraint, then dense param detail; almost every clause earns its place. It is somewhat over-packed into long lines and the trailing sentence is truncated ('It also rewrote …'), which slightly hurts readability.

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 mutation tool with no output schema and a nested object param, it covers the input contract, required fields, and server-side side effects thoroughly. It omits nothing critical, though it does not address response shape or auth/permission expectations.

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?

Reported schema coverage is 0% at the top level, and the description compensates by inlining the full CalendarEventInput shape with formats ('HH:MM', IANA zone, enum meter|kilometer|yard|mile) and the critical rule that only name/date are required. It stops short of explaining every field's semantics (e.g. url, note), leaving some room, but adds substantial meaning over the raw schema.

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?

Opens with a specific verb+resource ('Adds a race or other event to the calendar') and immediately scopes behavior ('Always stored PRIVATE'). An agent can distinguish this creation tool from siblings like update_calendar_event, list_calendar_events, and get_calendar_event without opening any schema.

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?

Usage is implied by the create semantics but the description never states when to choose this over update_calendar_event or schedule_workout, nor any prerequisites. The inclusion of the raw endpoint hints at integration context but does not guide tool selection.

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