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 value by explaining the importance of PTR records for email sending reputation, which is useful context beyond the annotations, though it doesn't detail rate limits or specific behavioral traits.

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, front-loaded with the core purpose and followed by additional context about email reputation. Every sentence adds value without redundancy, making it efficient and well-structured.

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 (single parameter, 100% schema coverage, annotations covering key behaviors), the description is complete enough for a read-only lookup operation. However, without an output schema, it could benefit from mentioning the return format (e.g., hostname or error), but the context provided is adequate for basic use.

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 ip_address parameter fully documented in the schema. The description does not add any parameter-specific details beyond what the schema provides, so it meets the baseline of 3 without compensating with extra semantic information.

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 ('Reverse DNS lookup') and resource ('Find the hostname associated with an IP address'), distinguishing it from siblings like dns_lookup or mx_lookup by focusing on PTR records specifically. It adds context about email reputation, which further clarifies its unique purpose.

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 for reverse DNS lookups related to email reputation, but does not explicitly state when to use this tool versus alternatives like dns_lookup or when not to use it. It provides clear context but lacks explicit exclusions or named alternatives.

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