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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the agent knows this is a safe read operation. The description adds valuable behavioral context beyond annotations by detailing which specific sources are included (World Bank, IMF, DBnomics fallback, ECB, FRED disabled) and that it provides attribution lines, giving the agent concrete expectations about output content.

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 a single sentence but packs substantial information without fluff. It front-loads the core purpose ('The official sources behind StatCite') and then details the sources and what each offers. The sentence is slightly dense with parentheticals, but every clause earns its place; it is concise yet comprehensive.

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?

Given the tool's simple nature (no parameters, no output schema), the description is fully complete. It states exactly what will be returned: the list of sources, what each covers, its license, and the attribution line. There is no ambiguity about the tool's function or expected output, and the low complexity means no additional details are needed.

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?

With zero parameters, the schema provides no semantics to explain. The description doesn't need to add parameter meaning because there are none. Per the rubric, a baseline of 4 is appropriate for tools with no parameters, and the description gives sufficient context about what the list will contain.

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 clearly states the tool's purpose: listing official sources, their coverage, licenses, and attribution lines. It uses specific action verbs ('List') and resource types ('data sources, licenses, and attribution rules'), and distinguishes itself from sibling tools like compare_sources by focusing on enumeration rather than comparison.

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 makes the usage context clear: it is the go-to reference for understanding what sources exist behind StatCite, what they cover, and how to cite them. While it doesn't explicitly exclude alternatives or name sibling tools, the guidance is implied strongly enough that an agent would know when to call it (e.g., before citing or when source availability is in question).

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