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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds genuine behavioral context that annotations cannot: notes and labels are included, conversations are filtered to the caller's AI access scope, and the response carries a label_version token required by update_labels. It still says nothing about behavior when contact_id is unknown or out of scope.

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 dense sentence with no filler, and the resource itself is front-loaded. It is slightly run-on with three nested parenthetical clauses, but every clause carries 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 an output schema present, the description need not explain return values, and its brief enumeration is a useful complement. For a one-parameter, read-only lookup this is close to sufficient, but the complete absence of id-sourcing and not-found behavior leaves a real operational gap.

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% and the sole parameter contact_id is never mentioned in the description, so the numeric-string pattern, where to obtain an id, and what happens with an out-of-scope id are all undocumented. The description does not compensate for the schema gap at all.

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 is a noun phrase enumerating the return payload (notes, current labels, WhatsApp conversation ids) rather than stating a verb, but it does make clear that a single contact record is fetched. It never contrasts with search_contacts or search_messages_and_contacts, so the agent must infer that this is the single-record lookup rather than a search.

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?

No when-to-use or when-not-to-use guidance is given, and no alternative sibling (notably search_contacts, for finding a contact when the id is unknown) is named. The only usage signal is the implicit workflow hint that the returned label_version token feeds update_labels.

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