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

Annotations already declare write/destructive/idempotent/openWorld, but the description adds genuine behavioral constraints the annotations cannot express: a one-hour validity window, refusal when the event was changed by someone else since the original call, and the underlying endpoint. These are exactly the failure modes an agent needs to anticipate.

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 tight sentences, front-loaded with the WRITE marker, then the required input, then the constraints and endpoint. No filler and nothing buried.

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 one-parameter mutation tool with no output schema, the description covers input provenance, time limit, and conflict behavior. It stops short of saying what a successful undo returns or whether any state is left behind after the one-hour window lapses.

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 100% and the single undo_id parameter is fully documented there, so baseline is 3. The description adds only the provenance of the id ('from that call'), which slightly reinforces but does not meaningfully extend the schema.

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 (undo) and resource (a recent event creation, update or deletion), plus the exact identifier needed. It is clearly distinguishable from the sibling mutation tools (create/update/delete_event) and even names the operations it reverses.

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 makes the trigger condition clear: it is used with the undo_id returned by a prior create/update/delete call, so an agent knows to reach for it only after one of those operations. It doesn't explicitly name a sibling as the alternative path (e.g. 'to make a new change, use update_event'), so it stops short of full when/when-not routing.

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