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

Adds real behavior beyond the annotations: date/time/timezone changes reset every invitee's answer and notify them, and version is the last-seen value (optimistic concurrency). Annotations only declare non-readonly, non-destructive, idempotent. It still doesn't say what happens on a stale version conflict, so not a 5.

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 dense sentences, front-loaded with what can be changed, then the consequence. Slightly obscured by referencing 'plan.starts_local', a field name that does not appear in the input schema (which uses starts_at), which costs a point.

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 an 11-parameter mutation with an output schema and safety annotations, the description covers the main logical fields and the key side effect. Gaps remain on ends_at and on invitee add/remove behavior, but nothing critical to calling it correctly is missing given the schema descriptions that do exist (timezone, idempotency_key).

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 only 27% across 11 parameters, so the description must carry weight. It adds meaning for version and, implicitly, timezone (change resets answers), but never mentions ends_at, add_invitees/remove_invitees semantics, or how partial updates are treated. Partial compensation for a large coverage gap.

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?

Names a specific verb (changes) and resource (a plan) and enumerates the mutable fields: date, time, place, title, description, invitees. The scoping phrase 'a plan the agent organizes' distinguishes it from respond_plan (answering an invite) and cancel_plan among the many plan siblings.

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?

Usage is implied by the field list but never stated as when-to-use/when-not, and no alternative sibling (e.g. respond_plan, cancel_plan, update_group) is named as a routing option. The only decision-relevant note is that a date/time/timezone change resets answers, which nudges but does not direct tool selection.

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