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

Annotations already declare this is a destructive, non-idempotent mutation, so the description does not need to restate safety basics. The description does add useful context that changes are applied against a number revision, implying versioned updates, but it does not say whether updates are partial merges or replacements, what happens on revision mismatch, or what permissions are required.

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 single sentence is front-loaded and free of filler, with no repetition of annotations or schema metadata. It is appropriately concise, though the terse phrasing around 'number revision' could be clearer.

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 destructive six-parameter update with zero schema parameter descriptions, the description is thin. It does not explain number_id, the revision-based concurrency model, whether unspecified fields remain unchanged, or how to recover from a stale revision; the presence of an output schema offsets only the return-value gap.

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 0%, so the description must compensate for six undocumented parameters. It names label, inbound, outbound, retained, and revision conceptually, but omits number_id entirely and gives no detail about optionality, allowed values, or the meaning of revision beyond 'number revision'.

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 uses a specific verb, 'Change', and names the settings affected: label, inbound/outbound availability, and retention preference. It is clear what the tool does, but it does not explicitly differentiate this mutation from nearby tools such as get_phone_number_settings or set_default_phone_number.

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 only usage signal is 'using the number revision', which implies a prerequisite but does not explain where to obtain the revision or what happens if it is stale. There is no guidance about when to choose this tool over sibling update or settings tools, nor any when-not-to-use condition.

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