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

Goes beyond the annotations by disclosing the guest-notification side effect, the fact there is no silent-cancel path, the confirmation default, and the Cotlet API key requirement. These are genuine operational details not captured by readOnlyHint/openWorldHint/destructiveHint.

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 guest-notification point is stated three times in different wording ('Partiful notifies the guests', 'Guests are notified', 'Partiful has no way to cancel without telling them'), which bloats an otherwise short description. Front-loading is fine but there is meaningful redundancy.

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 single-parameter mutation with no output schema, the description covers the important behavioral facts an agent needs: it mutates state, notifies guests, requires confirmation, and needs an API key. Nothing critical for correct invocation is missing.

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?

Only one parameter (event_id) and schema description coverage is 100% ('Event ID from list_events'), so the schema carries the load. The description adds nothing about the parameter, making the baseline 3 appropriate.

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 (cancel) and resource (event) and the outcome is unambiguous. It does not need to distinguish from within-app siblings since Partiful has no other cancel tool, but it spends several sentences restating the same action rather than sharpening it.

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?

Clearly conveys the confirmation policy ('By default you confirm each call; you can switch that off') and the human-impact guidance ('confirm with the user before each call'). No alternative tool is named because none exists, so there is no exclusion guidance to give.

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