list_lines

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

With no annotations, the description carries the behavioral burden. It conveys a read-only listing operation, scopes it to US mobile lines, states the sort order, and implies that returned items include a lineId for use in other tools. It stops short of describing output fields or pagination, but for a zero-parameter list this is sufficient.

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 no filler. The core behavior is front-loaded, and the second sentence adds the cross-tool usage note. Every word earns its place.

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 listing tool, the description covers scope, ordering, and how the result feeds sibling tools. The lineId mention compensates for the absence of an output schema by giving the agent the most important detail it needs.

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 accepts no parameters, so the schema is fully complete and there is nothing for the description to add. The 0-parameter baseline of 4 applies.

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 names a concrete operation ('List'), a specific resource ('US mobile lines'), and the workspace scope ('API key's workspace'), plus the ordering ('newest first'). This is clearly distinguishable from sibling tools about messages and codes, so an agent knows exactly what this tool returns.

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 sentence 'Every other tool takes a lineId from here' is an explicit when-to-use instruction: call this first to obtain a lineId before using sibling tools. No alternative listing tool exists among the siblings, so the guidance is complete.

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