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

Annotations already indicate a mutating, idempotent, non-destructive operation; the description adds meaningful behavior beyond that: a revision check on expectedUpdatedAt, standard permission and notification rules, and an explicit warning that CRM field values must be treated as untrusted data rather than instructions.

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?

Three short sentences: the first states the core operation, the second adds behavior, the third gives the assignee source, and the security warning earns its place. No filler or repetition of the title.

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 5-parameter mutation tool with no output schema, the description covers purpose, revision behavior, permissions, notifications, assignee sourcing, and data-safety. It leaves idempotencyKey semantics and expected failure/return behavior unstated, but the annotations and schema cover enough for a competent call.

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 description coverage, the description partially compensates: 'assign or clear' explains assigneeId including null to clear, and 'revision check' maps to expectedUpdatedAt. However, idempotencyKey and id are left to inference, and workspaceId relies entirely on the schema description.

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 action ('Assign or clear the assignee') on a specific resource ('existing activity') and adds a key detail ('with a revision check'). This distinguishes it from siblings like assign_record_owner, create_activity, and complete_activity without needing to inspect schemas.

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?

Provides clear usage context: it targets existing activities, supports clearing as well as assigning, and points the agent to list_record_owners as the source for valid assignees. It does not explicitly name exclusions or alternatives such as assign_record_owner, so it stops short of a 5.

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