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

Annotations already establish readOnly/idempotent/destructive=false, so safety is covered. The description adds meaningful scope beyond that: it is CONUS-only (excluding OCONUS/foreign), and it discloses the returned components (breakfast, lunch, dinner, incidental, first/last travel-day amounts), which is valuable given there is no output schema.

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 tight sentences with zero filler, front-loading the resource and scope before the sibling routing instruction.

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 single-parameter read-only tool with annotations covering the safety profile, the description supplies scope (CONUS), returned fields, and routing to the companion tool. Nothing critical is missing, though it could note OCONUS handling more explicitly.

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% and the single fiscal_year parameter is already documented in the schema, including its range and publishing window. The description only restates 'federal fiscal year' without adding format or edge-case detail, so the 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?

States a specific verb (List) and a well-defined resource (CONUS M&IE tiers for a federal fiscal year), then enumerates the exact amounts returned. It clearly distinguishes itself from the gsa_per_diem_lookup sibling by naming it explicitly.

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 second sentence routes the agent: use gsa_per_diem_lookup to find the applicable total for a destination, implying this tool is for inspecting the tier structure itself. This is a clear contrast with an alternative, though it stops short of an explicit when-not condition for this tool.

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