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

Adds real context beyond the annotations: payment is processed through the owner's own Stripe, archive permanently retires the plan (consistent with destructiveHint=true), and the call returns one of three stripe states including an onboarding_url. That last detail is useful routing information an agent could not infer from readOnlyHint=false / destructiveHint=true alone. It stops short of explaining what happens to existing subscribers when a price changes.

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 compact sentences that front-load the action and the modes, with zero filler. The telegraphic fragments ('archive retires it') trade a little readability for density, 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?

Output schema exists, so the brief return note is a bonus rather than a requirement, and the mutation semantics are signaled by annotations. Still, for a destructive, non-idempotent billing tool with a nested price object, the description omits the required site/plan inputs and any statement about the effect on already-subscribed users or how to proceed after needs_onboarding.

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 50%, and the description does clarify the intent of three params: free (the free plan), price (paid via the owner's Stripe, monthly or yearly), and archive (retires the plan). But the required 'site' and 'plan' parameters and 'name' get no elaboration, and the cents-vs-pence currency unit hint lives only in 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?

Specific verb pair ('creates or changes') plus a specific resource ('an app plan'), enumerating the three plan shapes (free, monthly/yearly price, archive). It is clearly distinct from near-name siblings like save_list, save_group, and save_app_list because the resource is named, though it never explicitly contrasts with them.

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?

Usage is implied by the enumerated modes (free plan, priced plan, archive to retire), which lets an agent infer roughly when to call it. There is no explicit when-to-use/when-not-to-use statement, no prerequisite or permission guidance, and no named alternative for related operations such as setup_app.

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