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

Annotations already declare readOnly, idempotent, non-destructive, and openWorld, so the safety profile is covered. The description adds only the vague 'bounded' notion of pagination and says nothing about the required private API key, rate limits, or what a bounded result set actually means (limit/cursor behavior).

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, front-loaded with the operation and scope, with no redundant or filler text. Every clause contributes either scope or intent.

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 correctly compensates by enumerating the returned fields. Filters and auth are left to the schema, and pagination behavior is only gestured at, so it is near-complete but not fully self-sufficient.

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 description coverage is 83%, so baseline is 3. The description's field list loosely maps to the state enum values (paid, pending, past_due, failed), but it adds nothing about limit, cursor, or begin_time/end_time semantics 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?

The description uses a specific verb+resource ('Return bounded Recurly invoices') and enumerates the fields returned, making the scope concrete. It separates itself from rec_url siblings like recurly_list_accounts/subscriptions/transactions by resource name, though it never explicitly contrasts 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?

'Answers which customer balances are paid, pending, past due, or failed' implies the query use case, and pairs naturally with the state enum. But there is no explicit when-to-use/when-not guidance and no mention of the sibling tools or of choosing list vs. other lookup paths.

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