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

Annotations already declare readOnlyHint=false, destructiveHint=false and non-idempotent, so the safety profile is covered; the description adds the genuinely useful part — the persistent consequence that this calendar's events will block bookings. It does not state whether re-selecting is harmless, how to undo it, or what permissions the connected credential needs.

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?

One sentence, no filler, with the action and its consequence front-loaded. Nothing could be cut without losing meaning.

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 mutating, non-idempotent, non-destructive selection tool with four parameters and no output schema, the description covers the effect but omits reversibility and idempotency guidance. An agent could call it correctly but would not know how to undo or repeat it safely.

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 75%, so most parameters are already documented with their source (list_calendars). The description adds no parameter-level meaning, and delegationCredentialId remains undocumented in both places; baseline 3 applies.

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 effect: adding a connected calendar to the set that blocks bookings during busy-time checks. This distinguishes it reasonably well from connect_calendar_with_credentials and list_calendars, though it never contrasts with the obvious inverse sibling unselect_calendar or with set_destination_calendar, which also assigns roles to calendars.

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?

"when checking for busy times" implies the context of use but gives no explicit trigger, prerequisites, or exclusion. It never mentions that unselect_calendar reverses this, or that externalId/integration/credentialId must first come from list_calendars (that detail lives only in the schema).

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