mailX tools

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

Annotations already provide readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true, covering safety and idempotency. The description adds minimal behavioral context by noting the impact on email deliverability, but doesn't disclose details like rate limits, authentication needs, or what 'popular' blacklists entail. No contradiction with annotations.

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 two sentences that are front-loaded with the core purpose and efficiently explain the impact. Every sentence adds value without redundancy, making it appropriately sized and well-structured for quick understanding.

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 tool's low complexity (1 parameter, no output schema), good annotations, and high schema coverage, the description is mostly complete. It covers the purpose and impact, but could improve by specifying which blacklists are checked or providing more behavioral details, though annotations help fill some gaps.

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 description coverage is 100%, with the parameter 'domain_name' fully documented in the schema as 'The domain name or IP address to check against blacklists, e.g. example.com or 1.2.3.4.' The description doesn't add any parameter-specific information beyond what the schema provides, so it meets the baseline for high coverage.

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 specific action ('Check if a domain or IP address is listed') and resource ('popular email blacklists (DNSBLs)'), distinguishing it from sibling tools like dns_lookup or spf_check which perform different DNS-related operations. It also explains the practical impact ('can severely impact email deliverability'), adding context beyond the basic function.

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 implies usage context by mentioning 'email deliverability,' suggesting this tool is for email-related blacklist checks, but it doesn't explicitly state when to use it versus alternatives like smtp_check or dns_lookup. No exclusions or specific alternatives are named, though the context is clear for email-focused scenarios.

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