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

Annotations already flag readOnlyHint=true; the description adds value by detailing what each entry contains (number, saved name or absent name, country) and explicitly disclosing that block dates are unavailable because WhatsApp does not report them. This avoids the agent expecting a timestamp that will never appear.

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?

Three short sentences carry the action, output semantics, and a notable data absence without redundancy. The core purpose is front-loaded and every sentence 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 one-parameter read-only list with an output schema and readOnly annotation, the description is complete: it names the scope, explains the returned fields, and flags the missing date. An agent has everything needed to invoke and interpret the call correctly.

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 100% and the single account_id parameter is already documented as 'the account whose blocklist to read, as returned by wa_list_accounts.' The tool description adds no parameter-specific detail beyond that, so the baseline score is appropriate.

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 opens with a specific verb and resource: 'List every contact one of your accounts has blocked.' It clearly distinguishes this read-only listing from siblings like wa_list_contacts (all contacts), wa_block_contact, and wa_unblock_contact by focusing on the blocklist.

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 intended context—reading a specific account's blocklist—is clear from the description and the account_id schema note. However, it never states when to prefer this tool over wa_list_contacts or wa_search_contacts, nor does it mention when not to use it, so the guidance is implied rather than explicit.

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