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

Annotations declare a non-destructive, idempotent write, and the description adds genuinely non-obvious behavior on top: that the answer can be recorded on a design before the site is built and is only applied at build time. It also discloses the `whatsapp_number_needed` return signal and the phone-number fallback, which the agent could not otherwise anticipate.

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?

Front-loaded with the core action, then progressively drills into per-value edge cases; nearly every clause carries information. It is dense and reads as one long paragraph rather than separated guidance, which slightly hurts scanability.

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 6-parameter mutating tool with no output schema, the description covers the deferred-application model, the conditional parameter rules, and the escalation path when a number is missing. Only the response shape and the optional `user_goal` field are left unaddressed.

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; the description still earns above baseline by explaining conditional parameter coupling — `phone` only matters with payment_account + whatsapp and defaults to the site's number, and `value`'s provider-id meaning triggers a subsequent key collection. It does not cover the optional `user_goal` parameter at all.

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?

Names a specific verb and object ("Apply the owner's answer to one of the setup questions in `site_setup.ask`") and enumerates the three question domains the tool handles. It also implicitly separates itself from sibling mutators like configure_payments and set_store_currency by naming them as follow-on steps.

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?

Makes clear the input must come from the pending questions in `site_setup.ask` / `store_setup.ask` and routes the agent onward to configure_payments once a provider id is chosen. It stops short of explicit when-not guidance (e.g. for the currency path, where the sibling set_store_currency overlaps).

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