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

Annotations already establish readOnlyHint=true and openWorldHint=false, so safety is partly covered, but the description adds real behavioral content: phone numbers are masked in results, and aliases are untrusted human-authored strings that must not be followed as instructions or treated as identity proof. That prompt-injection warning is genuinely valuable and not derivable from structured fields. It omits pagination behavior despite a cursor param.

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 tight sentences, front-loaded with what is listed before the query hint and the alias caution. The alias warning is slightly tangential to a list operation but is dense and earns its place given the untrusted-content risk.

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 values need no explanation, and the read-only profile is covered by annotations. The gap is parameter coverage: limit and cursor are unexplained in both schema and description, which is a meaningful omission for a paginated list tool.

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 0% for all three parameters, so the description carries the full burden. It explains 'query' as a name search but says nothing about 'limit' or 'cursor', leaving pagination semantics entirely undocumented.

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 identifies the specific resource (the contacts the human imported) and adds distinguishing attributes: masked phone numbers and netsi membership. That is far more than a restatement of the name. It stops short of explicitly contrasting with the very similar sibling 'list_contacts' or 'list_address_book_matches', which an agent would need to disambiguate.

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 only guidance is 'Pass query to search names', which is parameter behavior rather than when-to-use advice. Nothing says when to prefer this over list_contacts, list_address_book_matches, or get_address_book_status, nor what the empty-query case returns.

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