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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds value beyond that by disclosing what the payload contains (per-session attendance counts, cancelled/moved status, leader summary) and the leader-only scope, which are not encoded in any structured field. It repeats 'Read only' but adds real behavioral context.

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?

Front-loaded with the resource and its contents, then closes with the practical `key` hand-off and read-only note. Dense but every clause carries information; only the redundant 'Read only.' line is strictly expendable given the annotations.

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 shape needn't be explained, yet the description still orients the agent on what to expect. For a 2-parameter, none-required, idempotent read with full schema coverage and clear sibling routing, nothing an agent needs to call it correctly 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?

Schema description coverage is 100% — both `week` (date format, default this week) and `group` (name/groupId, optional when exactly one group is led) are fully documented in the schema. The description adds nothing about parameter syntax beyond what the schema provides, so baseline 3 applies.

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 and resource ('A group's week as its leader sees it') and enumerates the contents (sessions with dates, times, places, cancellation status, attendance counts, and a leader summary). The scoping phrase 'For a group the person LEADS' distinguishes it from leader-agnostic siblings like events or list_upcoming, so an agent can route without opening schemas.

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 concrete downstream routing: 'Use the session's `key` with who_is_coming and change_session.' It also states the access precondition (must lead the group). It does not explicitly say when NOT to use it versus read_household_calendar or events, so it stops short of a 5.

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