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

Annotations already provide readOnlyHint=true, and the description reinforces this with 'Read'. It adds useful behavioral details beyond annotations: cross-account scope, oldest-first ordering, and the pagination pattern using next_cursor. No contradictions with the annotation.

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, each contributing: purpose and ordering, pagination mechanic, and a concrete use case. No filler or redundancy, and the most important information is front-loaded.

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 present and annotations covering read-only behavior, the description supplies everything an agent needs to call the tool correctly: scope, ordering, pagination, and when to use it. No critical gaps remain.

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 baseline is 3. The description adds value beyond the schema by explaining how to use after_cursor in conjunction with the output's next_cursor for pagination, clarifying the intended pattern more concretely than the schema alone.

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 states a specific verb ('Read'), resource ('messages'), and scope ('across all your WhatsApp accounts') with ordering ('oldest first'). This clearly distinguishes it from sibling list tools like wa_list_calls or wa_list_contacts.

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?

It gives clear context: 'Use this to catch up after being notified of a new message' and explains pagination via after_cursor. However, it does not explicitly name alternative tools for fetching messages from a specific chat, so it lacks full when-not-to-use guidance.

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