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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds value by specifying the exact data elements returned and the CONUS scope, which goes beyond the annotations without contradicting them.

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 succinct sentences: the first states purpose and data fields, the second routes to the sibling tool. No wasted words, and key info is front-loaded.

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 simple list tool with one parameter and annotations covering safety, the description is complete enough. It tells what fields are returned and references the sibling for totals. It doesn't address edge cases like invalid fiscal years or availability, but these are minor for such a straightforward tool.

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?

The input schema already describes fiscal_year completely (four-digit federal fiscal year, current three years). The description does not add any new meaning to the parameter, so it provides no extra semantic value beyond the schema. Baseline 3 is appropriate given 100% schema coverage.

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 ('List') and resource ('CONUS meals-and-incidental expense tiers'), and enumerates the exact data returned (breakfast, lunch, dinner, incidental, first/last day amounts). This clearly distinguishes it from siblings like gsa_per_diem_lookup, which retrieves a total.

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 explicitly names the alternative tool (gsa_per_diem_lookup) and the condition for using it (to identify the applicable total). While it implies this tool is for breakdown details, it doesn't explicitly state 'use this when you need the M&IE breakdown,' so the guidance is clear but not fully explicit.

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