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

No annotations are provided, so the description must carry the burden — and it does well: it discloses ZIP+4 normalization, multi-destination result behavior without auto-selection, fallback to Standard CONUS when no non-standard destination exists, and the verification_url output. It omits error/invalid-ZIP behavior and any rate-limit or freshness caveats beyond 'today's rates'.

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?

Front-loaded with purpose, then progressively details multi-destination handling and path semantics. Mostly earns its space, though the ZIP/ZIP+4 normalization sentence duplicates the schema and could be trimmed.

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 explains return contents (seasonal lodging rate and M&IE rate) and multi-result behavior, which is sufficient for correct use. It lacks error-case handling, but the core information an agent needs to call and interpret the tool is present.

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 the baseline is 3. The description adds real meaning beyond the schema by stating the default behavior when `date` is omitted (today's rates) and reinforcing ZIP+4 normalization, which materially helps invocation.

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 ('Return every GSA destination rate') and resource (per diem rates by ZIP code and date). Scope is precise and distinguishes it from siblings like get_gsa_perdiem_by_destination or get_gsa_perdiem_by_state by naming ZIP-code and single-date targeting.

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?

Gives clear operating context: date is optional with a stated default, and multiple destinations per ZIP are explained with a suggested disambiguation approach (county or geocoder). It does not name sibling alternatives (e.g., the year-based variant) or exclusions, so it falls short of full when/versus guidance.

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