Get MyFatoorah invoice

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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds useful behavioral detail beyond that, particularly the exact endpoint routing and the fact that external identifier lookup returns the most recent matching invoice. No contradiction with annotations.

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 sentences with no filler. The purpose is front-loaded, and each clause carries distinct information: the lookup constraint, the invoice-ID path, and the external-identifier path with its recency behavior.

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?

The tool has only two parameters, an output schema, and annotations covering safety and idempotence. The description provides the remaining necessary operational details, including endpoints and the semantics of external identifier lookups, so an agent has everything needed to call it correctly.

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 only 50%, with lookupBy having no description beyond its enum. The description compensates by mapping lookupBy values to specific endpoint paths and clarifying that externalIdentifier resolves to the most recent matching invoice, adding meaning 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 action, 'Gets an invoice', and precisely defines the two lookup modes with endpoint paths. The resource (invoice) is clearly distinct from sibling tools that retrieve payments, refunds, or payment methods, so an agent can select it without ambiguity.

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 description clearly conveys when this tool is appropriate: when an invoice needs to be retrieved by exactly one lookup type. It does not explicitly name alternatives or exclusion conditions, but the sibling tools are organized by resource, making the intended context evident.

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