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

Annotations already establish readOnlyHint=true, so the safety profile is covered; the description adds the entitlement constraint (Coach Pro / gym tier) that an agent needs to interpret failures. Return payload is only sketched as '(name, size)' with no pagination or ordering notes.

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 short sentences with no filler, and the returned-field summary is front-loaded before the tier caveat. Nothing can be cut without losing information.

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 must cover return values, and it does so minimally (name, size), plus the access gate. For a zero-param read tool that is close to sufficient; ordering, pagination, and empty-state behavior are unstated.

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?

Zero parameters, so the baseline is 4 and there is nothing the description needs to disambiguate. The '(name, size)' note describes output rather than input, which is harmless but not parameter semantics.

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 the resource precisely ('the coach's client groups') and the fields returned (name, size), which separates it from the singular get_client_group. It is a noun fragment rather than an explicit verb and never explicitly contrasts with list_groups_for_client, so it stops short of a 5.

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 supplies a real precondition — groups are a Coach Pro / gym feature and free coaches hit errors on the write tools — which tells the agent the read is gated. But there is no guidance on when to choose this over get_client_group or list_groups_for_client.

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