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

Annotations already mark this as read-only, idempotent, and non-destructive DNA, and the description adds critical behavioral context: the returned link opens a Stripe payment page, nothing is charged unless the user pays, and existing subscribers see the dashboard plan page. This goes well beyond the annotations and clarifies the external side effects.

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?

Two dense, front-loaded sentences cover the main return content and the critical side-effect behavior without fluff. Every clause earns its place, and the most important information appears first.

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?

For a single-optional-parameter tool with no output schema, the description is complete: it explains what is returned, how the optional parameter changes the result, and what happens when the link is opened. No essential calling information 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%, so the baseline is 3. The description's parameter-related explanation ('the next plan up when none is given') directly mirrors the schema description for the optional plan field)Skip no additional meaning beyond 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 states a specific verb and resource: it 'Returns PostWire's paid plans' including price, inclusions, current plan, and a checkout link. It clearly distinguishes the tool as a plan/upgrade helper rather than a general account or post-management tool.

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?

The description clearly conveys the use case: showing plans and obtaining an upgrade/checkout link, with an explicit behavior for omitting the plan parameter. It does not name alternatives or explicit exclusions, but the context is unambiguous enough for an agent to select it appropriately.

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