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

Annotations cover destructive/idempotent/openWorld, and the description adds substantial context beyond them: both assignees get notifications, the assignee owns the calendar event and Google Calendar side-effects email attendees, stale_revision on concurrent change, and idempotency replay semantics. This is exactly the kind of behavioral disclosure that goes beyond structured hints.

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 the core action, then prerequisites, side-effects, and concurrency/idempotency in a logical order. It is dense but each sentence carries information; the appended injection-warning sentence is standard but slightly detracts from focus.

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 destructive multi-param mutation with no output schema, the description covers side-effects, required precondition fields, error behavior (stale_revision), and idempotency. It leaves workspaceId usage implicit, but otherwise an agent has what it needs to call it correctly.

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?

With only 20% schema coverage, the description compensates well: it explains assigneeId's source (list_record_owners) and that it can be cleared, expectedUpdatedAt (from get_activity), and idempotencyKey replay behavior. Only workspaceId is left to the schema's own description, keeping it just short of a 5.

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 and resource ('Sets or clears the assignee of one activity'), including the replace semantics ('replacing the current one'). This lets an agent distinguish it from the sibling assign_record_owner (which assigns owners to records) and update_activity.

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?

It gives clear operational guidance: take the member id from list_record_owners and reassign only on the user's instruction. It stops short of explicitly contrasting when to use this versus update_activity or assign_record_owner, so it is clear context without full alternatives coverage.

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