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

Beyond the annotations, the description discloses optimistic concurrency behavior (stale_revision), a required dependency on get_activity, and a security-relevant instruction that CRM field values must be treated as data, not instructions. These are meaningful behavioral details not present in the schema or annotations.

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?

The description is compact and front-loaded: the first sentence states the action and scope, the second covers the concurrency requirement, and the third lists exclusions. The security note is a single sentence and earns its place. No filler or redundant restatement of the tool name.

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 update tool with no output schema and low schema coverage, the description covers the essential call requirements: required fields, the expectedUpdatedAt dependency, stale_revision behavior, and immutable fields. It does not explain all possible data field value formats or idempotencyKey usage, but the core invocation context is sufficiently complete.

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 description coverage is only 20%, so the description must compensate. It does so by listing the updatable fields and explaining expectedUpdatedAt's role and source. It does not describe value types or the idempotencyKey semantics, but the main data parameter is substantially clarified.

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 clearly states the tool updates one activity and enumerates the specific fields that can be changed (title, description, location, startAt, dueAt, etc.). It does not explicitly differentiate from sibling tools like update_record or complete_activity, so it falls short of a 5.

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?

The description gives a clear prerequisite: expectedUpdatedAt must come from get_activity, and it warns that stale_revision is returned if the value changed. It also explicitly lists what cannot be changed (assignee, attendees, recurrence, record links), providing a when-not boundary, though it does not name alternative tools.

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