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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely new context beyond that: the tool is free, requires no API key, and returns each format with a per-operation capability matrix rather than a bare name list.

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?

A single sentence that front-loads what is returned and then qualifies it with the capability set and the zero-cost/zero-auth note. No filler or redundant restatement of the title.

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 zero-parameter, read-only listing tool with no output schema, the description tells the agent what the result contains (formats plus per-operation capabilities) and that no auth or cost is involved. That is everything needed to call it correctly.

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 takes zero parameters, so the baseline is 4 and there is no parameter meaning for the description to supply. The schema is empty and consistent with a discovery/catalog call.

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 names a specific verb (Lists) and resource (every e-invoice and bank statement format Klarbon handles), and adds that each entry carries capability flags (open, check, convert from, convert to, make). This clearly separates it from the action siblings like check_invoice or convert_invoice, though it doesn't name any sibling 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?

There is no explicit when-to-use statement or routing to alternatives; usage is only implied by the capability verbs (an agent would infer calling this before convert_invoice to discover supported formats). The 'Free, no API key needed' note hints at a low-cost discovery call but is not framed as guidance.

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