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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds useful non-obvious constraints: times must carry a timezone offset and timezone is required. It does not describe return shape, pagination, or slot ordering, but the annotations lower the bar sufficiently for a solid 3.

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?

Five short sentences, front-loaded with the purpose, then the workflow position, then the identifier rules, then the timezone constraint, then the negative scope. Every sentence carries distinct information with no repetition of the schema.

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 an 8-parameter read tool with annotations and no output schema, the description covers the highest-risk ambiguities: identifier selection and timezone formatting. Minor gaps remain around when duration matters and the effect of rescheduleUid, though the schema documents both.

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 coverage is 88%, so the baseline would be 3, but the description adds meaning the schema only implies piecemeal: the event type is identified either by eventTypeId alone or by eventTypeSlug plus usernameList. That combinatorial constraint is the main source of invocation errors and the description surfaces it directly.

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?

States a specific verb and resource (find open booking slots for an event type) with explicit scope boundaries (between start and end). It names sibling tools create_booking and reschedule_booking, so an agent can place it in the workflow 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?

Gives explicit ordering guidance ("Call this before create_booking or reschedule_booking") and a clear negative boundary ("This only returns slots. It does not book or notify anyone"), which tells the agent both when to use it and what it will not accomplish.

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