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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=true), but the description adds genuinely useful context the annotations lack: the security model (a group grants nothing until a rule names it), the required role (Owner or Admin), and the membership precondition. It does not discuss return shape or what happens on duplicate names.

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?

Three terse sentences, each carrying distinct information: what it creates, how it relates to rules, and the operational prerequisites. Front-loaded with the core purpose and no filler.

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 no output schema, the description should carry the return expectations, and it does not say what the call returns (e.g., the new group id). Everything else an agent needs to invoke the tool correctly, permissions, membership constraint, relationship to rules, is present, so the gap is minor.

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%, so the schema already defines both name and userIds, and the description adds no syntax or format detail beyond them. The one behavioral hint, "only members who have joined can be added," constrains userIds but is framed as a requirement rather than a parameter explanation. Baseline 3 is 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?

The description states a specific verb and resource ("Creates a group of members") and immediately distinguishes it from the closely related rule concept with "A group grants nothing until a rule names it." An agent can tell this apart from create_access_rule and list_access_groups without opening either 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?

It gives clear context and prerequisites: "Mirrors New group on Settings › Roles & access; needs Owner or Admin. Only members who have joined can be added." That tells the agent the permission bar and the membership constraint. It stops short of naming when-not-to-use or a sibling alternative, so not a 5.

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