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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description still adds real value by disclosing output constraints (counts only, no PII exposed) and the recovery path for a disconnected address book, which the annotations do not convey.

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 short sentences, front-loaded with the returned fields, followed by the privacy constraint and the remediation note. Each sentence carries distinct information, though the closing iPhone detail is slightly incidental.

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 value structure need not be re-explained. For a no-argument read tool with annotations covering safety, the description supplies the return content, its PII limits, and the disconnected-state path — everything an agent needs.

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 the baseline of 4 applies; there is nothing for the description to disambiguate. Schema coverage is 100% and no parameter documentation is needed.

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?

States a specific verb (get) and resource (address book status) and enumerates exactly what is returned: connection state, last import/match timestamps, and contact/people counts. The 'Counts only: no names, no numbers' clause implicitly but clearly separates it from sibling list_address_book, which returns actual contacts.

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 rather than stated: an agent can infer this is the lightweight status/count check versus list_address_book or list_address_book_matches, but the description never names those alternatives or says when to prefer one. The 'If it is not connected...' sentence is remediation guidance, not a when-to-use rule.

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