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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, which the description aligns with by saying 'Read'. The description adds behavioral details beyond annotations: the query is a substring on name/phone and the default limit is 50. No contradictions, and these extras enhance transparency.

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 concise, using two sentences plus a structured list of actions and a flattened action note. It avoids redundancy and conveys essential information efficiently without unnecessary verbosity.

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?

Given the tool is a list action, the description covers the core functionality (reading contacts, searching, default limit) and aligns with annotations. It does not explain the return format (no output schema present), but it omits details like the 'account' parameter. Overall, it is sufficiently complete for a list operation, though not exhaustive.

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?

The schema has no parameter descriptions, and the description only partially explains the parameters. It clarifies 'query' (optional, substring on name/phone) and 'limit' (default 50), but 'jid' and 'account' remain unexplained. Since coverage is below 50% and the description fails to compensate for all parameters, the score is low.

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 reads WhatsApp contacts and explicitly lists two actions (list and get), with the flattened action being 'list'. It distinguishes from the 'get' action which provides full info by JID, and mentions searching with an optional query, making the purpose specific and unambiguous relative to siblings like whatsapp_contacts_get.

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 implies usage by stating 'search across contacts' and mentions 'get: full contact info by JID', which hints at when to use this tool vs the get variant. It also notes the default limit of 50, providing pagination guidance. However, it does not explicitly contrast with other sibling tools (e.g., chats, groups) but the context is sufficient.

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