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

With readOnlyHint=true, the safety profile is already known, but the description greatly exceeds that by detailing every billing state, the meaning of days_until_next_transition, the null behavior for comped accounts, and the fact that books remain safe and ingesting even when walled. It also discloses that payment_url is for humans only.

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 description is dense and front-loaded with the core purpose and the never-blocked guarantee. It is long, but nearly every clause adds actionable state or operator guidance; only minor restructuring could improve scannability.

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?

Given an output schema already exists, the description need not explain return values. It completely covers all billing states, transition timing, special comped behavior, and payment instructions, leaving no obvious gap for an agent selecting or invoking the tool.

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 the only parameter org_id is already well documented with default behavior and matching constraints. The description does not need to add more, so the baseline 3 is appropriate.

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 clearly identifies the resource as 'This organisation's billing state' and explains that it works in every state and can explain payment_required errors from other tools. This makes it distinct from sibling tools like get_books_status or get_financial_summary, even without naming 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?

It explicitly says the tool is never blocked and should always be used when other tools return payment_required. It also tells the agent exactly what to do in key states, such as telling the operator to subscribe, and warns never to attempt payment completion.

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