finish_change_number

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

With no annotations, the description carries the full burden. It discloses the linked-device failure, the permanent migration on success, the updating of linked devices, and the pin condition. It does not mention failure scenarios (e.g., wrong code) but is otherwise thorough.

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 paragraph but logically ordered: purpose, condition, prerequisite, parameter details, success effect, and a final warning. Every sentence contributes essential information, with the most critical constraints placed early.

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 two-step process with device restrictions and conditional pin, the description covers all necessary context: the prerequisite call, the device limitation, the success outcome, and explicit guidance on when to use. No output schema exists, but the description suffices for correct invocation.

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 coverage is 100%, so the schema already describes parameters. The description adds extra context: number in E.164 format, 6-digit code, and the conditional nature of pin, which enriches the schema definitions.

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 explicitly states the tool's purpose: completing the second step of a Signal number change by submitting the verification code. It clearly distinguishes from the sibling start_change_number by naming the step and the prerequisite.

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?

Provides explicit usage guidance: must be called after start_change_number, warns not to call without it, explains the primary-device requirement, and specifies when to include the pin. This fully addresses when-to-use vs alternatives.

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