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

Annotations already flag destructiveHint=true and idempotentHint=true, and the description adds the non-obvious context behind them: a one-switch-per-30-days budget is consumed, the LRU account is locked until a stated date, and nothing changes in Google Ads. It explains why the operation is not freely repeatable, which the annotations alone cannot convey.

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?

Three dense sentences front-load the cost and consequence before the precondition, which is the right order. Phrasing like 'switching back included' and the quoted notice string are slightly cryptic, but nothing is wasted.

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?

With no output schema and one parameter fully documented, the description covers everything an agent needs: the trigger, the user-consent requirement, the quota cost, the side effect on another account, and the no-op case. Nothing material is missing for a destructive, quota-limited mutation.

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% and the single parameter's description already specifies the format and source (from list_accounts). The prose only adds that customer_id is the account that becomes active, a small increment over the schema, so baseline 3 is appropriate.

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 and resource (switch the plan's active account) and goes further to describe the concrete effect: customer_id becomes active and the least recently used active account locks. No sibling tool overlaps with this behavior, so an agent can identify it immediately.

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 precondition – call only after another tool returned an "Account switch:" notice for this account and the user agreed – plus the exemption that it is a no-op for an already-active account. This is exactly the when-to-call/when-not detail an agent needs for a rare, quota-limited action.

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