List DID numbers

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

The readOnlyHint annotation already communicates that this is a safe read operation. The description adds useful detail about the included fields (number, active status, tenant, contact) but does not disclose additional behavioral traits such as ordering, pagination, or scope limitations. This is consistent with the annotations, and the added value is moderate.

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 one efficient sentence that front-loads the primary action and resource, then lists the returned fields. Every word adds value, with no redundancy or filler.

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 list tool, the description is complete: it explains what is listed and what fields will be present in the result. Annotations cover the read-only and open-world aspects, and the output field enumeration compensates for the lack of an output schema.

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 there is no parameter burden for the description to carry. The schema coverage is 100% by virtue of having an empty parameters object, and the description appropriately focuses on the output rather than input semantics.

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 states a specific verb ('List'), a precise resource ('DID (inbound phone) numbers'), and the scope ('on the PBX'). It also enumerates the key fields returned, making the tool's purpose unmistakable and clearly distinct from sibling tools like list_extensions or list_providers.

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 gives clear context: use this when you need DID numbers and their related details on the PBX. It does not explicitly name alternatives or exclusions, but the resource type is distinct enough that an agent can infer when to select this over the sibling list tools.

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