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

Goes well beyond the annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false, openWorldHint=false) by disclosing the invitation cap, the yes/no/maybe response model, mutual visibility of attendees ('everyone invited sees who is coming'), and the non-push delivery model ('Nothing is pushed: they find it the next time their agent checks the inbox'). It also points at plan.starts_local as the value to read back, which is behavioral guidance no annotation carries.

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?

Four tight sentences, front-loaded with the action and its scope, then delivery semantics, then the confirmation prerequisite. The final sentence about plan.starts_local is the only slightly cryptic line and would benefit from being tied to the response rather than dangling.

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?

With an output schema present, return values need not be explained, and the description covers the collaboration semantics, delivery behavior, and the leave_in_inbox branch. It omits any mention of the escape hatch for a wrong plan (cancel_plan/update_plan) and gives no sense of failure modes when a handle does not resolve.

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 50% and five of the eight fields carry good inline descriptions (starts_at, ends_at, timezone, invitees, idempotency_key). The description reinforces the confirmed input set (title, date/time, time zone, place, invitees) and the 30-invitee cap, but adds little syntax or format meaning beyond what the schema already supplies. Baseline 3 fits.

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 and resource with scope: 'Makes a plan with a fixed date and invites up to 30 of your contacts'. The following sentences clarify that this is an invitation-with-RSVP flow, which separates it from create_invite, create_group and respond_plan without opening any schema.

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 an explicit routing rule away from a sibling ('A message without a date is leave_in_inbox') plus a prerequisite workflow ('The title, date and time ..., place and invitees are confirmed with the person first'). An agent knows both when to call this and when not to.

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