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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds a genuine content trait—results include pending invitations—but says nothing about ordering, pagination, or response shape, so the added value is modest.

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?

A single compact sentence with no filler, and the key content detail (pending invitations) is stated up front. Every clause earns its place.

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 a no-param, read-only list tool with full annotation coverage, the description tells the agent what comes back (groups, plus pending invites). Without an output schema, a bit more on item structure or ordering could help, but nothing essential 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?

The tool takes zero parameters, so there is no parameter semantics burden on the description; the schema (empty, additionalProperties=false) is fully self-documenting. Baseline 4 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?

Specific verb ('Restituisce') plus resource ('gruppi di contatti dell'utente'), and it adds scope detail by noting pending invitations are included. It doesn't explicitly distinguish itself from siblings like contacts.search or contacts.get, 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?

The listing purpose implies when to use it (enumerating the user's contact groups), but there is no explicit when/when-not guidance or named alternative for related lookups such as contacts.search. Usage is only inferable.

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