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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuinely useful context beyond them: the returned link is 'same-origin' and the actual billing mutations occur elsewhere on the website, telling the agent this call does not itself change anything.

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 short sentences, front-loaded with the core action and followed by the one constraint that matters. Nothing is padded or repeated.

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 simple read-only link getter with annotations covering safety and no output schema, the description is close to adequate, but it leaves three enum parameters and the return value's form unexplained. It should do more given the 0% schema coverage.

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 description coverage is 0%, so the description must carry parameter meaning, but it never mentions intent, plan, or interval. The enum values are self-describing to a degree, yet the required 'intent' and its interaction with plan/interval are left entirely to inference.

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?

States a specific verb and resource ('Get a same-origin link to the billing page or plan selection'), so an agent immediately knows this returns a link rather than performing billing. It does not reference any sibling, but unlike get_plan_usage its domain (billing/plan link) is unambiguous.

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?

'Billing actions happen in the website' implies the intended flow: use this to obtain a redirect target, then let the user act on the site. It does not state when to prefer this over other paths or which intent values map to which scenario, leaving usage largely inferred.

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