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

Annotations declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint. The description adds 'resolve/verify the recipient' context, which is useful but does not go beyond what annotations imply. It doesn't mention rate limits, caching, or exact data returned, but with annotations covering the safety profile, a 3 is appropriate.

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 main description is one sentence, efficient. The account_id parameter has a lengthy but useful explanation. The overall structure is clear, but the parameter descriptions add extra detail that, while helpful, could distract from the main description.

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 2 parameters and no output schema, the description is complete enough for an agent to call it correctly. It explains the identifier requirements, the resolution purpose, and the acaccount_id handling. It might benefit from noting that phone numbers must be in E.164 format, but the current detail is adequate.

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 100%, so the schema already describes both parameters including the user_id and account_id. The description clarifies that user_id must come from a resolver and never be a display name or URL, and guides on account_id selection when multiple accounts exist. This adds valuable meaning beyond schema.

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 'Retrieve a WhatsApp user profile' and specifies the input identifiers (provider user ID or phone number), distinguishing it from other WhatsApp tools like whatsapp_list_contacts or whatsapp_is_number_registered. It could be slightly more specific about what fields are returned, but the purpose is unambiguous.

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 description says 'Use to resolve/verify the recipient before a new chat', providing clear context for when to use this tool. It does not explicitly mention when not to use it or name alternatives, but the purpose is clear enough among siblings.

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