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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds useful context in the form of the underlying REST mapping (GET /numbers) and the returned field set, but says nothing about pagination behavior or ordering even though page/per_page exist. With annotations carrying the safety burden, this is a modest but real contribution.

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 tight sentences with the core purpose and returned fields front-loaded, followed by the REST endpoint mapping. No filler, though the endpoint string is marginal value for an agent that is not calling the API directly.

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?

With only two optional params, no required params, and no output schema, the description compensates reasonably by listing the returned fields. It is nearly complete; only pagination/ordering behavior is left unstated, which the schema partially covers.

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?

Schema description coverage is 100%, with both page and per_page fully documented including defaults and max in the schema itself. The description adds no parameter-level meaning (e.g., how pagination interacts with large number sets), so the baseline 3 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?

States a specific verb and resource ('List the phone numbers owned by the company') and even enumerates the returned fields (id, name, digits, country), so the agent knows exactly what this returns. It does not explicitly distinguish itself from the sibling aircall_get_number (single-number lookup), though the plural 'list' vs 'get' makes that reasonably inferable.

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?

Usage is only implied by the verb and scope; there is no explicit statement of when to prefer this over aircall_get_number or how it relates to listing other resources. No exclusions or prerequisites are given. Adequate but leaves the alternative-selection decision to inference.

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