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

Goes well past the readOnlyHint annotation by naming the required key scope (billing:read or billing:write) and the non-blocking behavior ('It does not wait: call again after a while'). It also enumerates the observable states and the recovery_url surfaced on action_required, which is exactly the behavior an agent needs to plan around.

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-loads read-only and scope, then the return values, then the action guidance. The parenthetical state enumerations are long but functional since there is no output schema. Every sentence carries information, though the nested parentheses make it denser than ideal.

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 carries the return-value burden and does so: it lists all request and contract states and mentions recovery_url. Combined with the deployment gate and polling instruction, an agent has everything needed to call and interpret it.

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 both parameters are already documented, including the default-to-latest-request behavior the description repeats. The description adds the provenance link (request_id that plan_set returned), which is mildly useful, but no format or edge-case detail 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?

States a specific verb and resource pair: returns request state and the site's contract state, plus the key constraint. It is clearly distinct from plan_show/plan_profile in content, though it never names a sibling to contrast with, so it stops short of a 5.

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?

Explicitly says to omit request to get the latest, what to do once applied (you can deploy), what to do on action_required (hand recovery_url to the user), and that it doesn't wait so it must be re-called. Missing only an explicit 'use plan_show instead when...' comparison, but the polling and follow-up guidance is strong.

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