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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and openWorldHint=false, so the safety profile is covered. The description adds nothing beyond that: no return format (image URL, base64, binary?), no fallback behavior when the contact has no avatar, no note on whether a connection/auth is required.

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 with no filler. It is efficient, though its brevity edges into under-specification rather than being a model of compactness.

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 no output schema, the description is the only place to explain what is returned (an image URL? binary payload? null if absent), and it omits that entirely. For a lookup tool whose whole value is the returned avatar, this is a meaningful 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 100%, so both parameters are documented, and the schema already says chat_id is a 'Contact or group ID'. The description's phrase 'of a contact or group' confirms group IDs are accepted but adds little beyond the schema — baseline 3.

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?

States a specific verb ('Get') and resource ('avatar of a contact or group'), which is clearly distinct from siblings like whatsapp_get_contact_info or whatsapp_get_group_data. It stops short of explicitly differentiating itself from those tools, so it lands at 4 rather than 5.

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?

There is no guidance on when to call this versus whatsapp_get_contact_info or whatsapp_get_group_data, no prerequisites (e.g., contact must exist, instance must be connected), and no exclusions. The agent must infer all of that.

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