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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful behavioral context: the returned account_id is a prerequisite for other tools, and the 'connected' state is a usability condition. However, it doesn't describe the output structure or whether disconnected accounts are still listed, which would be useful given the state caveat.

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 earning its place: what it does, why to call it first, and the connected-state constraint. Front-loaded with the action and resource.

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 zero-parameter read-only list tool, the description covers the essential context: what it returns conceptually (accounts), why it matters (account_id prerequisite), and a usage condition (connected state). The output schema exists, so return values need not be described. Minor gap: it doesn't state whether disconnected accounts appear in the list, but the state caveat implies they may.

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 tool has zero parameters, so the schema is trivially complete. The description adds no parameter details because none are needed. Baseline 4 for zero-param tools 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?

States a specific verb ('List') and resource ('WhatsApp accounts available to you'), and distinguishes itself from the many sibling tools by being the account-listing tool. The description also clarifies scope ('available to you'), which is more specific than a generic list.

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?

Explicitly instructs the agent to call this first because every other wa_ tool needs an account_id from here. This is strong when-to-use guidance and implicitly excludes using other tools before this one. It also adds a usage condition: an account is only usable while its state is 'connected'.

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