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

The description is exemplary in disclosing critical behavioral traits: the key is returned only once and cannot be recovered, only a SHA-256 hash is stored, and it explicitly instructs the agent to show the key verbatim and tell the user to save it. This goes far beyond the annotations, which only provide basic hints. The 100 documents/month limit also adds valuable context.

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 concise yet complete, with a clear front-loaded purpose. The critical warning is emphasized with caps and a dash structure. Each sentence contributes: purpose, usage context, security warning with actionable instruction, and constraint. No wasted words.

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 single-parameter tool with no output schema, the description covers the most essential context: the purpose, the constraint, and the irreversible key return. It could explicitly state the output format, but the instruction to 'show it to the user verbatim' implies the key is returned in a usable form. This is nearly complete.

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 schema already provides complete coverage for the only parameter, email, including a format and description. The tool description reinforces the one-key-per-address rule but does not add technical details beyond the schema. Baseline 3 is appropriate since the schema handles the semantics fully.

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 opens with a specific verb and resource: 'Mint a free Attestwire API key'. It clearly differentiates this from sibling tools by explicitly stating that this key enables validate_invoice and generate_invoice. The scope (100 documents/month, no signup flow) adds precision.

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 states 'so validate_invoice and generate_invoice can be used', which establishes when this tool is needed. It also provides constraints like 'One key per email address' and sets expectations with 'no signup flow, no card'. It doesn't explicitly mention alternatives because no alternative exists, but the context is clear.

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