Show signed-in phones

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

The readOnlyHint annotation already signals a safe read operation. The description adds useful behavioral context: the scope 'on this device' and the automatic refresh of login codes when using other tools. This goes beyond the annotation by explaining session lifecycle behavior, though it does not detail edge cases like empty lists or exact return format.

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 two sentences, front-loaded with the action, and every part adds value. The first sentence states purpose and output; the second adds a relevant behavioral note about automatic refresh. No wasted words.

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 tool with no output schema, the description adequately explains what it does and what it returns (phone numbers and expiry times). It also provides session refresh context. It lacks explicit formatting details but is sufficiently complete for the tool's simplicity.

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?

With zero parameters, the schema provides no parameter details. The description inherently explains the tool's scope ('on this device') and output (phone numbers and expiry times), which is the baseline expected for a parameterless tool. No additional parameter semantics are needed.

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 lists phone numbers signed in on this device and includes session expiry times. It uses a specific verb ('List') and resource ('signed-in phones') that distinguishes it from sibling tools like login_send_sms, login_confirm, and logout.

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 what it does, but it does not explicitly say when to use it versus alternatives. The note about login codes refreshing when using other tools hints at session management context but does not provide direct guidance such as 'use this to check active sessions before logging in'.

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