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

With no annotations provided, the description must carry the full burden. It declares 'Read-only' and explains the default behavior when the filter is omitted, which is genuinely useful, but it says nothing about the shape of the returned catalogue, whether plans and add-ons are separate sections, or authentication requirements.

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 compact sentences with the resource and contents front-loaded, followed immediately by the filter semantics and safety trait. 'etc.' is the only soft spot and it costs nothing in practice.

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 one-parameter read tool with no output schema, the description covers what is returned (plans plus add-ons with prices), the filter, and the read-only nature. Only the structure of the returned catalogue remains unspecified, which is a minor gap given the tool's simplicity.

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 enum is already documented, so the baseline would be a 3. The description adds real value beyond the schema by stating that omitting the parameter returns every currency, which is the key decision an agent must make when invoking.

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: listing public plans and add-ons with prices, with concrete examples (Extra Agent Slot, SDR sender pair). The word 'public' implicitly separates it from account-scoped tools like get_subscription and get_balance, but no sibling is named explicitly.

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?

The currency-filter behavior is spelled out clearly ('omitted = every currency'), but there is no explicit guidance on when to choose this tool over get_subscription, get_balance, get_balance_full, or get_supported_currencies, all of which live nearby and could be confused with pricing lookups.

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