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

Annotations already declare destructive=true, idempotent=true, and readOnly=false, so the safety profile is covered. The description adds two things the annotations cannot express: cancelling notifies everyone invited, and human confirmation is required beforehand. It still does not state whether the cancellation is reversible or what happens to existing RSVPs.

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?

Two short sentences, zero filler, with the action and its blast radius front-loaded before the consent requirement. Every clause earns its place.

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?

An output schema exists so return values need not be explained, and annotations cover the safety profile; the description supplies the missing side-effect and consent context. The only real gap is routing guidance versus sibling tools like respond_plan, which matters for a plan-management surface this crowded.

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 50%; plan_id is self-describing via its uuid format and pattern, and idempotency_key is fully documented in the schema. The description contributes only the implicit narrowing 'a plan you organize,' which slightly constrains which plan_id is valid but adds no format or validation detail.

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 (cancels) and resource (plan), and adds a meaningful scope qualifier — 'you organize' — which separates it from plans the agent merely participates in. It does not explicitly name the neighboring alternatives (respond_plan, update_plan, leave_group), so it falls just 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?

Gives one real prerequisite: 'Confirm with your human first,' which is actionable usage guidance for a destructive call. However it never says when NOT to use it or which sibling to reach for instead (e.g., declining an invite via respond_plan rather than cancelling), leaving the alternative-selection logic to inference.

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