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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description still adds non-obvious context beyond them: that the call costs nothing ('Free') and that authentication is required, which are genuine behavioral facts an agent needs.

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?

Three short sentences with the main purpose front-loaded and no padding. The 'Free.' fragment is terse but conveys a meaningful fact efficiently.

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 lookup with no output schema, the description covers what it returns, what it costs, and what auth it needs. Only minor gaps remain (e.g., currency/format of the balance), which is acceptable at this complexity.

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; there is nothing for the description to clarify and it does not attempt to misdescribe inputs.

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?

States the specific resource returned: the user's current credit balance. The verb ('get'/'retrieve') is implied rather than stated, and it doesn't differentiate from cotlet_whoami or other cotlet_* account tools by name, but the resource is unambiguous.

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?

'Free' signals there is no cost/credit consumption to calling it, and the auth prerequisite ('needs the user's Cotlet API key or sign-in') tells the agent what is required before calling. There is no explicit when-to-use vs. alternative guidance, leaving usage implied.

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