list_accounts

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

The description explains what the tool returns (E.164 phone number and registration status) and implies it is a read-only operation. No annotations are present, so the description carries the full burden; it is transparent enough for a simple list tool, though it could explicitly state it is read-only.

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 concise, consisting of three sentences that sequentially cover the action, the return format, and usage guidance. Every sentence adds value, and the structure is efficient.

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?

The tool has no parameters and no output schema, so the description sufficiently covers its functionality, return values, and typical usage context. It explains the common scenario (single account) and purpose, making it fully complete for an agent to select and invoke the tool correctly.

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 input schema has zero parameters, so the baseline is 4 per the rubric. The description does not need to add parameter information; it instead describes the output, which is appropriate for a parameterless tool.

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's purpose: to list all Signal accounts with their phone numbers and registration status. It distinguishes from the sibling tool 'get_own_number' by noting that the latter is for single-account setups, ensuring the agent knows which tool to use.

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 explicitly advises when to use this tool ('when you need to confirm which accounts are available before sending or receiving messages') and when to use an alternative ('Use get_own_number to get the active account's number in single-account setups'), providing clear usage guidance.

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