finish_change_number

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

Annotations only supply generic hints (readOnlyHint=false, idempotentHint=false, openWorldHint=true). The description adds concrete behavior beyond them: primary-device-only restriction with the literal failure message, irreversibility ('cannot be undone except by another change-number round'), and error semantics for a wrong PIN ('fails with the number of tries remaining').

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 step-2 framing and prerequisite are front-loaded, and each sentence carries a distinct fact (prereq, params, device restriction, consequence, error behavior, return value). It is dense rather than padded, though the run-on single paragraph could be split for faster scanning.

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?

No output schema exists, yet the description documents the return value ({status: 'number changed', number}), the prerequisite, the side effect, and the failure modes. For a 3-param, irreversible multi-step tool this covers everything an agent needs before calling.

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 baseline is 3, but the description adds real meaning the schema lacks: 'number' must be the same value passed to start_change_number, and 'pin' is conditional on a Registration Lock being set. It stops short of adding format nuances beyond E.164, which the schema already states.

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 (submits the verification code) plus the exact scope: it is step 2 of moving this Signal account to a new phone number. It explicitly positions itself relative to the sibling start_change_number ('Call start_change_number first'), so an agent can separate the two-step flow without opening either schema.

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 an explicit prerequisite ('without it there is no code to verify') and names the alternative path for the optional PIN parameter ('needed only if one is set (see set_pin)'). It also states the when-not condition: primary device only, failing on linked signal-cli setups.

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