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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description's added value is disclosing return content (provider per identity, and 'what it can do'), which matters because no output schema exists, but it says nothing about ordering, volume, or pagination.

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?

A single front-loaded sentence that leads with the verb and then enumerates the resource types in order of specificity. Every clause earns its place by telling the agent exactly what comes back.

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 no output schema, the description does the work of explaining the return payload: identity types, supplying provider, and capabilities. That is sufficient to call the tool correctly, though the absence of any usage routing leaves the sibling-choice decision to the agent.

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?

Only one optional parameter (include_shared) at 100% schema description coverage, so the schema already carries the meaning. The description does not mention the shared-numbers option or clarify its business-account scope, so it adds nothing beyond the structured field; this is the expected baseline when the schema is complete.

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 (returns) and enumerates the exact resources covered: phone numbers, caller IDs, verified SIMs, PBX extensions, and eSIMs, scoped to 'this Widely seat'. It is distinguishable from narrower siblings like list_did_numbers or list_pbx by being a superset, though it never names those siblings explicitly.

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?

No guidance on when to use this tool versus alternatives such as list_did_numbers, list_pbx, or search_numbers, and no prerequisites or conditions stated. The 'on this Widely seat' phrasing hints at scope but the agent must infer that this is the comprehensive listing tool.

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