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

With readOnlyHint=true already covering the safety profile, the description adds useful behavioral context beyond the annotation: the endpoint selection behavior and the site-wide default scope. It stops short of describing pagination/response shape, but that is not critical for a read-only list tool.

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 tight sentences carry the full message: the first states purpose and scope, the second states the account_id endpoint condition. No filler, and the most important information is front-loaded.

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 tool with seven optional parameters, all covered by the schema, and a readOnly annotation, the description explains the one non-obvious behavioral choice (account-scoped vs site-wide endpoint) and leaves parameter details to the schema. The absence of an output schema is acceptable because the list semantics make the return shape predictable.

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 adds extra value by explaining that account_id changes the API endpoint and that state filtering is available, which goes beyond the individual parameter descriptions.

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 names a specific action ('List') and resource ('subscriptions'), and immediately characterizes scope ('across the site, optionally scoped to one account and/or filtered by state'). This clearly distinguishes it from single-subscription get_subscription and mutating cancel/pause siblings.

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 gives direct conditional routing guidance: provide account_id to hit GET /accounts/{account_id}/subscriptions, otherwise GET /subscriptions, and state can be used as a filter. This is clear context for when to use the tool, though it does not explicitly contrast with sibling tools like get_subscription.

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