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

Annotations declare readOnlyHint=false with a mutating path, and the description explains exactly that: read-only by default, a plan change only with start_trial, and no payment ever taken. It also discloses the local-install browser side effect, adding context beyond the annotations.

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?

Front-loaded with what the tool shows, then the behavioral caveats, with no filler. Slightly repetitive in restating that the user follows the link to pay, but it is tight overall.

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 3-optional-param tool with no output schema, the description covers default behavior, the mutating branch, payment safety, and the local-install variant, so an agent has everything needed to call it correctly.

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, but the description adds meaning the schema doesn't carry: start_trial is a plan change that takes no payment, and open is a local-only branch that the hosted server ignores in favor of returning the link.

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 uses a concrete verb set (show plan, remaining quota, unlocked features, upgrade link) rather than restating the name. It is clearly distinguishable from every sibling, none of which touch billing or plan state.

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 explicitly tells the agent to call it any time, not just after a limit, and spells out the exact conditions that change behavior: start_trial=true starts a trial, while open=true matters only on local installs. It also states what the tool will not do (upgrade a paid plan, take payment), which is precise routing guidance.

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