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

With no annotations, the description carries the burden well: it discloses the one-to-many ZIP-to-destination behavior, that no destination is auto-selected, the Standard CONUS fallback for non-standard ZIPs, and ZIP+4 normalization. It omits auth/rate-limit context, but for a read-only lookup the behavioral disclosure is notably above average.

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?

The core capability is front-loaded in the opening sentence and each following paragraph adds a distinct, non-redundant fact. It is slightly long for a three-parameter lookup, but no sentence is filler.

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 does the necessary work of explaining what comes back — monthly lodging rates for the fiscal year, the M&IE rate, and a `results` collection covering every applicable destination. Only response-shape details (field names, ordering) are left implicit, which is minor.

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%, so all three parameters are already documented in the schema. The description reinforces ZIP+4 normalization and the fiscal-year definition but adds little syntax or format detail beyond what the schema states; baseline 3 applies.

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 names a specific verb and resource — GSA lodging rates for every month of a US fiscal year plus the M&IE rate for a ZIP code — which is unambiguous. It doesn't explicitly distinguish itself from near-siblings like get_gsa_perdiem_by_zipcode or get_gsa_perdiem_by_state_year, so an agent must infer the year-scoped variant is the differentiator.

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?

It gives useful downstream guidance (a ZIP can map to multiple destinations, the API won't pick one, use the county or a geocoder) and explains the Standard CONUS fallback. However, it never states when to prefer this tool over sibling tools such as get_gsa_perdiem_by_zipcode or get_gsa_perdiem_by_destination, leaving the choice to inference.

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