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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description still adds real value: the move is not instant, no sign-in is required, and crucially that this call does not start the move — a distinction an agent could easily get wrong.

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?

Four short sentences, all front-loaded, no filler. The telegraphic fragments ('No sign-in.', 'The move is not instant.') read abruptly but each carries distinct information, so little is wasted.

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 read-only quote with no output schema, the behavioral picture is adequate, but three of four parameters are undocumented in both schema and description, leaving an agent guessing at number/country/number_type formats.

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 only 25% (currency alone is documented), so the description carries the burden for number, country and number_type — and it supplies nothing beyond an implicit 'existing number'. It does not compensate for the coverage gap.

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: pricing a port of an existing number onto Widely, with the scope qualifier 'moving an existing number' that separates it from new-number quoting siblings. It doesn't explicitly name quote_number as the alternative, so it stops short of a 5.

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?

Gives a clear selection condition ('Use this when the current number should be kept') and warns against the misconception that it initiates anything ('This does not start the move'). It stops short of naming the sibling to use for a new number or for actually starting the port.

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