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

Annotations only give generic flags (destructive=true, idempotent=true, openWorld=true). The description adds substantive behavioral context the annotations cannot convey: no charge or refund for the current month, dropping a waiting switch by re-passing the current plan, the exact timing boundary for cancellation, the owners/admins-only authorization requirement, and the shape of the returned object including nextPlan.

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?

It is a single dense sentence with parenthetical asides, but every clause carries needed semantics (timing, billing, idempotence-by-re-pass, auth, return shape) and the mutation verb is front-loaded. Slightly heavy for one breath, but no wasted text.

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, the description explicitly covers what is returned and where the waiting switch appears (nextPlan), plus authorization and side-effect boundaries. For a two-parameter mutation tool this leaves nothing an agent needs to know 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 already 100%, so the baseline is 3, but the description goes further by explaining the effect of passing the current plan value (drops the waiting switch) and by compensating for the schema's zero required parameters with the 'Pass at least one' constraint. That is real meaning added over the schema.

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 opens with a specific verb and resource -- changing the workspace's monthly plan subscription -- and immediately scopes it to plan switches and cancellation flips, so it is clearly distinguishable from billing siblings like get_billing, list_credit_offers, and start_credit_checkout. An agent can tell what state this tool mutates without opening the 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?

It states the prerequisite 'Pass at least one' and describes the conditions under which each mode applies (plan switch from next renewal vs cancelAtPeriodEnd ending/resuming). It also names list_credit_offers as the source of valid plan values. It does not explicitly name alternative tools for adjacent billing actions, so a 4 rather than 5.

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