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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds a behavioral fact annotations cannot express: this call requires no authentication, which materially affects how an agent sequences it in onboarding flows.

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, zero filler. The core capability is front-loaded and the auth constraint plus the subscribe hand-off follow in priority order.

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 zero-parameter read with no output schema, the description covers what is returned (plans and prices), the auth posture, and the next step for subscribing. It omits any sense of the response shape (e.g., plan tiers, currency), which is the only remaining gap given no output schema exists to carry 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?

The tool takes zero parameters, so per the baseline there is nothing for the description to disambiguate. The description correctly implies a parameterless global fetch rather than a per-user lookup, which is the only semantic nuance available.

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: fetching 'oriiion's subscription plans and prices'. That is concrete and unambiguous. It does not, however, distinguish itself from adjacent billing/account siblings such as get_billing_status or get_ad_wallet, which an agent might reasonably consider for pricing questions.

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?

Gives an explicit use condition ('Works without authentication — useful before the user has an account') and routes the subscribe case to get_onboarding_links for the personal payment link. That is real routing guidance. It stops short of stating when not to use it (e.g., versus get_billing_status for an existing account's payment state).

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