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

No annotations provided, so the description carries full burden. It discloses that the email is discarded after verification, which is important behavioral info. Could mention error handling or side effects, but overall transparent.

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 sentences, each adding unique value: purpose, return data, and disposal. Front-loaded with the key action and 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?

With 2 required parameters and no output schema, the description adequately covers what the tool does, what it returns, and a key behavioral detail (email discarded). Could mention size limits or response format, but sufficient for the 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?

Schema coverage is 100%, baseline 3. The description adds value by specifying that 'eml' is base64-encoded and explaining its necessity for DKIM verification. It also clarifies the format of 'apiKey' with 'crk_...' prefix.

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 clearly states the tool's purpose: preview DKIM verification of a billing email without creating a spend or earning sats. It distinguishes from siblings like submit-receipt by emphasizing the preview nature and safety.

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 explains when to use the tool (preview before submission) and why the full email is required for DKIM verification. It implies not to use when intending to actually submit the receipt, but doesn't explicitly list alternatives beyond the context.

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