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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the description's real contribution is the disclosure that results are limited to the local cache and require no network — a material completeness caveat. It does not cover result ordering, pagination, or whether synced-but-unsent data is included, keeping it below 5.

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, front-loaded with the core action and scope, with each sentence carrying distinct information (scope, offline constraint, optional filter).

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 an output schema, full parameter documentation, and annotations covering safety, the remaining essential fact — that results are cache-bound — is stated. Only minor operational details (ordering, pagination limits) are absent.

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 documents query, limit, account, and chat_id. The description only echoes the chat_id restriction and adds no format or matching nuance beyond the schema's case-insensitive substring note.

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 (full-text search) and resource (WhatsApp chats), with the 'locally-cached only' qualifier that separates it from live-read tools like whatsapp_read_messages. It doesn't name any sibling explicitly, so it falls short of the top mark.

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?

Usage is implied by 'search', but there is no explicit when-to-use/when-not guidance or pointer to alternatives such as whatsapp_read_messages for browsing or whatsapp_sync before searching. The cached-only caveat hints at a precondition without stating it as one.

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