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

Annotations already establish read-only, idempotent, non-destructive behavior, so the description is not required to repeat that. It adds valuable behavioral context beyond annotations: update frequency ('updated each business day'), no authentication requirement, commercial use permitted, and a direct source (fiscaldata.treasury.gov). This gives the agent confidence about freshness and licensing that structured data does not convey.

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 description is compact and well-structured: purpose → return breakdown → update frequency → parameter guidance → data sample → source/licensing. Each sentence serves a purpose, and the most critical information (what the tool does) is front-loaded. The inclusion of a latest figure is optional but not bloating; overall it earns its place.

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 tool with a single optional parameter, rich annotations, and an output schema, the description covers all necessary context: source, licensing, update cadence, and breakdown structure. It does not need to explain return values because an output schema exists. An agent has everything required to call the tool correctly and interpret results.

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 has 100% description coverage for the single `days` parameter, including its range, default, and meaning. The description merely restates 'Specify `days` to retrieve a series (default 1 = latest day only)' without adding new semantics such as examples or behavioral consequences. With the schema fully covering the parameter, the baseline of 3 is appropriate.

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 opens with a specific verb and resource: 'Get the official US national debt figures from the US Treasury (Debt to the Penny).' It clearly distinguishes itself from sibling tools (e.g., treasuryfiscal.debt.expense) by specifying 'current' debt and the breakdown into public and intragovernmental holdings. An agent can confidently select this tool for current US debt figures without inspecting the schema.

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 provides clear context for when to use the tool: retrieve current national debt, optionally as a series via the `days` parameter. It does not explicitly name alternative tools or state when not to use it, but the specialized purpose ('current', 'debt', 'breakdown') makes the usage context unambiguous. No exclusions are stated, but they are not needed given the tool's narrow role.

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