list_numbers

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

With no annotations, the description carries the burden of behavioral disclosure. It explains meaningful semantics: each number can be assigned to one agent, agent_id=null means not answering inbound calls, and assigning an agent starts routing. It doesn't explicitly state read-only behavior, but the verb 'List' and the absence of side effects make that clear.

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 well-structured: a clear first sentence, a brief context paragraph, bulleted use cases, and a final behavioral note. Every sentence adds value, and the formatting makes it easy to scan.

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, this description is complete. It explains the domain, common use cases, field semantics, and connects to sibling tools like assign_number. An output schema exists, so return details don't need to be in the description.

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 baseline is 4. The description adds meaningful context about entity attributes like number_id, agent_id, and capabilities (voice, SMS), which informs the agent about the data model even though no input is 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 opens with a specific verb and resource: 'List all phone numbers provisioned in your organization.' It clearly distinguishes this list tool from siblings like list_agents or list_campaigns, and reinforces the purpose by explaining phone numbers are entry points for calls and caller ID.

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 'Use this to' bullet list explicitly states when to use the tool: finding number_id for make_call or create_campaign, checking agent routing, viewing capabilities, and finding unassigned numbers. It also provides an alternative action by referencing assign_number for null agent_id cases.

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