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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds the plan-requirement constraint and the exact endpoint, but says nothing about error shape, empty results, or whether inactive profiles are included.

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 compact sentences plus the endpoint, with the returned data front-loaded. Nothing is wasted, though the opening noun phrase reads as a fragment rather than a crisp statement of the operation.

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 one-parameter read-only lookup with no output schema and fully covered annotations, the description covers the returned content and the main precondition. Only the source of number_id and the failure mode for non-profile plans are left implicit.

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% for the single number_id parameter, so the baseline is 3. The description adds no meaning beyond the schema — it does not say where number_id comes from (e.g., placetel_list_numbers) or how it behaves.

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 the specific resource (routing profiles of a phone number) and the returned fact (which profile is active), which distinguishes it from the sibling action tool placetel_activate_number_profile. The verb is only implicit in the noun-phrase phrasing, but the GET endpoint and title make the read/list nature unambiguous.

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?

It supplies a real prerequisite ('Needs a Placetel plan with number profiles') that tells the agent when the call will fail. However, it never states when to use this versus placetel_activate_number_profile or how it relates to placetel_get_number / placetel_get_routing, so usage is only implied.

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