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

With no annotations, the description carries the full burden. It adds a genuinely useful behavioral detail: 'The key is shown once — store it.' But it doesn't disclose response format, whether the email must be vverified, or what happens on duplicate signup.

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 short sentences with no filler. The core action is front-loaded and the critical warning follows immediately.

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 one-parameter tool with no output schema, the description should explain both the required input and what is returned. It neither mentions email nor explicitly states the response contains the new API key, though 'key is shown once' partially implies it. Important gaps remain.

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 only parameter, email, is not mentioned in the description at all. Schema description coverage is 0%, and the tool description does not compensate by explaining what email is used for or how to provide it.

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 a specific verb and resource: 'Create an einvoicewiz API key'. cleary distinguishes from siblings like check_credits, create_facturx_pdf, and validate_einvoice — no other tool creates a key.

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?

Cleary implies when to use it: when a new API key with free credits is needed. No explicit exclusions or alternative mentions, but no sibling performs signup, so context is sufficient.

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