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

Beyond the read-only annotation, the description dictates key behavioral traits: it returns a 'graded verdict with prioritized fixes' and specifies how the output changes based on the 'detail' parameter being 'full' versus 'concise.' This adds significant operational context to the tool's execution.

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 dense but extremely efficient. It front-loads the primary value proposition and uses the remaining space to logically structure the differentiation from siblings and the parameter impact, without being verbose.

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?

Given the complexity of email security checks (multiple protocol checks, grading, and output toggles), the description is extremely complete. It provides all necessary context for an agent to determine if this is the correct tool to call and how to configure it.

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?

With 100% schema coverage, the description's job is to elaborate. It successfully adds meaning by defining the output difference between the 'full' and 'concise' detail options, helping the agent understand the scope of the returned data for each setting.

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 defines the tool's purpose: to answer if a domain is properly secured. It enumerates the checks performed (MX, SPF, DMARC, provider detection) and explicitly differentiates its function from a 'plain DNS resolver.'

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?

It provides comprehensive usage guidelines by specifying when to use the tool (e.g., 'when the user asks about email deliverability' or 'is email set up correctly') and providing explicit alternatives to avoid (e.g., 'dns_lookup, spf_analyze or dmarc_check'). It also points to 'dkim_discover' for DKIM specific keys.

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