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

Annotations already indicate destructiveHint=true, which warns of potential destructive effects. The description adds valuable context beyond this: it mentions that cancelling a shared plan can update existing guest copies and queue cancellation notifications, and that delivered notifications cannot be recalled. This clarifies side effects and limitations that are not captured in 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 concise, with three sentences that each serve a distinct purpose: usage guidance, exclusion/alternative, and behavioral warnings. The critical usage constraint is front-loaded, and there is no tangential content. Every sentence 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?

Given the tool's moderate complexity (2 parameters, 1 required), annotations, and the presence of an output schema, the description is largely complete. It covers the key use case, exclusions, and side effects. It does not explicitly describe the return value, but the output schema exists, so that is not required. The only minor gap might be assumptions about authorization or reversibility, but these are not critical enough to lower the score further.

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?

The schema covers 100% of parameters with descriptions, so the baseline is 3. The description does not add any additional parameter-specific details, but it does not need to since the schema is comprehensive for both parameters (timezone and planItemId).

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 identifies the tool's purpose: to delete, remove, or cancel an existing Familia plan item. It specifies the exact action and resource, and distinguishes itself from related actions like rescheduling or completing. This clarity makes it easy for an agent to match user requests to the correct tool.

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 explicitly states when to use this tool ('only when the user explicitly asks to delete, remove, or cancel an existing Familia plan item') and provides a direct exclusion: 'Do not use to reschedule or complete a plan; use familia_update_plan instead.' This naming of an alternative and the condition prevents misuse.

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