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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false, openWorldHint=false), so the description needs only to add context. It adds almost none: nothing about duplicate-name handling, whether creation is scoped strictly to the brand or automatic, or what the operation returns for the subsequent add-contacts step.

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 front-loaded sentence that names the action, its scope, and the downstream tools — no wasted clauses. The parenthetical about optional fields is slightly awkward but still informative.

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?

Missing: whether the created list's identifier is returned (critical, since whatsapp_add_contacts presumably needs it) and how duplicate names are treated. For a three-parameter creation tool with annotations and no output schema, this is a meaningful but not fatal 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 coverage is only 33%: brand_id is well documented in-schema (sourced from list_brands, with a disambiguation rule), but name and description have no schema descriptions. The tool description partly compensates by identifying name and description as the payload fields and noting description is optional, yet it omits the length constraints and any uniqueness expectation for name.

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?

Uses a specific verb and resource ('Crea una lista de contactos de WhatsApp') scoped to a brand, which distinguishes it from read-only siblings like whatsapp_list and from whatsapp_create_campaign. It also names the natural follow-up tool (whatsapp_add_contacts), so an agent can place it in the workflow without opening the schema.

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 workflow context is implied clearly enough: create the list here, add contacts with whatsapp_add_contacts, then use it in campaigns. However, it never states when NOT to use it — e.g. checking whatsapp_list first to avoid duplicate lists, or what to do if a list with that name already exists.

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