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

Annotations already establish read-only, idempotent, non-destructive safety, so the bar is lower; the description still adds real behavioral value by disclosing that both paid plans carry a 7-day free trial for new customers and instructing the agent to surface that to the person. It also notes that the optional business argument changes the returned information (which plan that page is on). It does not discuss error behavior for unknown handles.

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 three front-loaded sentences that move from what the tool returns to when to call it to the trial caveat, with no filler. The sentences are somewhat clause-dense and pack multiple instructions (route to upgrade_plan, disclose trial, pass business) into one paragraph, which slightly reduces 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?

An output schema exists, so the description need not document return values, and annotations cover the safety profile. It supplies the trial detail, the upgrade_plan handoff, and the optional parameter's effect, leaving only edge cases like invalid handles 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 schema already explains the business handle format, giving a baseline of 3. The description goes beyond that by explaining the effect of passing it: it reveals which plan the referenced page is on, information the schema does not convey.

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 first sentence states a specific resource and scope: what each Keepp plan costs and includes. It also names the sibling it hands off to (upgrade_plan), so an agent can distinguish the informational plan tool from the checkout tool 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?

It gives an explicit trigger ('call this when something needs an upgrade'), the goal ('so the person can choose knowing what they get'), and the next step in the chain ('then upgrade_plan for their checkout link'). The only missing piece is a when-not, which is minor for a read-only lookup.

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