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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower, and the description still adds meaningful behavior: the link opens a Stripe payment page in the browser, nothing is charged unless the user pays there, and existing subscribers are routed to the dashboard plan page instead. It stops short of link expiry or single-use semantics.

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?

The return contents are front-loaded in the first sentence, with the click-behavior caveat second. The first sentence is dense with a long parenthetical feature list, but no sentence 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, the description must carry the return-value burden, and it does: it enumerates plans, prices, plan contents, current plan, and the checkout link, plus what happens on click. Nothing an agent needs to call or interpret this tool is missing.

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 both params are enum-constrained with descriptions, so the schema already does the heavy lifting. The description restates the plan default ('next plan up') and interval meaning that the schema already documents, adding little beyond it.

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 names a specific verb and resource (returns paid plans, the current plan, and a checkout link) and enumerates the returned payload (monthly price, post/brand/AI-draft/network/scheduled-post limits). It is clearly distinguishable from siblings like my_account or get_x_credits, which do not surface plans or checkout links.

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 clear selection context: 'the next plan up when none is given' tells the agent the default when the plan parameter is omitted. It does not explicitly contrast with alternatives or state when-not-to-use, but the default behavior and interval default are well conveyed.

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