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

With no annotations provided, the description carries the behavioral burden. It discloses that the tool is authoritative and exhaustive ('Single source of truth') and warns against extrapolating beyond its output. The verb 'List' also implies a read-only operation, though it does not explicitly confirm absence of side effects.

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 concise sentences with no filler. The first sentence states what the tool returns; the second adds an important authority constraint. Every word contributes value.

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?

The description covers what the response contains (formats, tier limits, Pro features) and its authoritative nature. With no output schema, it could go slightly further in describing the response shape or grouping, but for a zero-parameter reference tool this is a minor gap.

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 tool has zero parameters and schema coverage is 100%, so there is nothing for the description to add about parameters. Per the calibration rule, this earns the zero-parameter baseline of 4.

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 uses a specific verb ('List') and a clear resource ('supported input formats'), and further specifies the content categories: per-tier limits and Pro feature requirements. This distinguishes it from sibling conversion and usage tools without requiring schema inspection.

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 'Single source of truth — do not claim capabilities beyond what this returns' sentence provides clear context: use this tool as the authoritative reference before asserting supported capabilities. It does not explicitly name sibling tools or spell out when not to use it, so it falls just short of full exclusionary guidance.

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