List your phones

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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint false, openWorldHint false), so the trailing 'Read-only' is redundant. The description still adds real context beyond the annotations: the online flag and last-seen timestamp let an agent reason about freshness before sending, and the deviceId linkage explains how the result feeds other tools.

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?

Two sentences with the resource and returned fields front-loaded, then the usage guidance. The only wasted words are 'Read-only', which merely restates the readOnlyHint annotation.

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 list tool with a rich annotation set and an existing output schema, nothing an agent needs is missing. It explains what is returned at a high level, why it matters, and how to use the result, without over-explaining.

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 takes no input parameters, so there is nothing to document on the input side and the baseline is a 4. The description still adds value by explaining that the returned phone ID is what other tools expect as deviceId, giving the output field a purpose.

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 and resource ('List the Android phones linked to the user's SMSTunnel account') and enumerates exactly what each entry contains: ID, name, online status, last-seen time. That is clearly distinct from siblings like get_message_status or list_received_texts, so the agent can pick it without opening a schema.

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?

Gives two concrete use cases (pick a phone and pass its ID as deviceId to send_sms or send_sign_in_code; verify a phone is online before sending) and names the downstream tools explicitly. This is exactly the when/when-not routing an agent needs.

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