Get subscription invoice

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

The annotations already fully declare the behavioral profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false, openWorldHint=true), so the safety bar is largely met without prose. The description itself adds no behavioral context beyond that – nothing about failure modes for a missing/foreign ID, the effect of the 'account' scoping or the 'include' expansion on visibility or latency.

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?

A single short sentence with the action and key front-loaded and no filler. It is efficient, though its brevity reflects thin content rather than disciplined editing.

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 read-only getter with a fully documented 3-parameter schema and rich annotations, the description is minimally sufficient to call the tool correctly. It is not sufficient to disambiguate among the dense cluster of subscription/invoice siblings, and with no output schema the agent also has no hint about what the invoice payload contains.

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 100%, so all three parameters (id, account, include) are already documented in the schema, which sets the baseline at 3. The description only echoes 'the given ID' and adds no format, ownership, or expansion 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 states a specific verb ('Retrieves') and resource ('subscription invoice') plus the lookup key ('with the given ID'), so the operation itself is unambiguous. It does not distinguish this tool from close siblings such as list_subscription_invoices, generate_subscription_invoice, or refund_subscription_invoice, which is what a 5 requires.

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?

There is no guidance on when to use this tool versus the many sibling invoice tools (list, generate, refund) or versus get_subscription. Nothing is said about prerequisites, such as the invoice needing to exist or the account/include context required to read it.

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