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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds valuable context about the tool's purpose and the behavioral rule about reusing the provider user ID, which goes beyond the annotations. It does not contradict any annotation.

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?

The description is two sentences with zero fluff, front-loading the purpose and immediately delivering the key usage instruction. Every word 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 list tool with no output schema, the description explains purpose and a key rule but omits output format and pagination behavior (limit/offset/cursor). It also does not mention that results are paginated or what fields are returned, which an agent would need for correct invocation. Annotations cover safety but not these operational details.

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 only 50% (limit and offset lack descriptions), and the description adds no parameter-specific meaning. It does not explain limit, offset, cursor, or account_id beyond what the schema provides, failing to compensate for the undocumented parameters. The 'provider user ID' is not a parameter here.

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 clearly states the tool lists WhatsApp contacts and explicitly ties it to resolving a human name/phone to an exact provider user identity before starting a chat. It distinguishes itself from siblings like whatsapp_list_conversations by focusing on contact resolution, and even gives a concrete usage directive (reuse provider user ID).

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?

It provides a clear when-to-use context (before starting a new chat) and a critical 'do not' instruction (do not pass display name as whatsapp_user_id). However, it does not explicitly name alternatives or when not to use this tool, though the use case is well implied.

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