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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the description benefits from a lower burden. It adds the workspace_revision prerequisite, but it does not disclose what changing the default affects, whether the prior default is overwritten, or any permission or reversibility implications. For a destructive mutation, this is a meaningful behavioral gap.

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 description is a single front-loaded sentence with no redundant or filler content. Every word earns its place by stating the action and referencing the prerequisite source for workspace_revision.

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?

An output schema exists, so return-value explanation is not needed, and annotations cover the safety profile. Still, the description omits what number_id represents and what effect changing the default has on existing configuration. It is minimally adequate but leaves gaps for a destructive operation with undocumented parameters.

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% with two required parameters, so the description must compensate. It explains where workspace_revision comes from, but it says nothing about number_id beyond the parameter name, leaving half the parameters without added semantic meaning.

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 states a specific action and resource: choose the default outbound phone number. It distinguishes the operation from general phone-number listing or updating siblings, though it does not explicitly name alternatives. The purpose is clear enough for an agent to identify the tool as the default-selection mutation.

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 gives a useful prerequisite by saying workspace_revision must come from get_phone_number. However, it does not state when to use this tool instead of update_phone_number or other phone-number tools, nor does it explain any exclusions. Usage context is implied and partially guided, but not fully explicit.

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