heade.rs

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

Annotations already cover safety (readOnly, idempotent, non-destructive, open-world). The description adds genuine behavioral context beyond those: data freshness ('live or mirrored within the hour') and latency ('a lookup takes a few seconds'). It stops short of describing failure/error behavior for invalid inputs, but the added traits are substantive.

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?

Front-loaded with the core purpose, then a structured per-input-type breakdown of return content. It is long, but nearly every clause enumerates a distinct data category rather than padding, so the length is largely earned.

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?

There is no output schema, and the description compensates thoroughly by enumerating what the report contains for each input type, plus freshness and runtime expectations. Nothing an agent needs to decide to call this tool and interpret its value is missing.

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%, and the schema itself lists the accepted query formats (domain, IPv4/IPv6, AS number, URL) and the format enum semantics (markdown vs json token cost). The description restates the query types and report size but adds no syntax or constraint detail beyond the schema, so the baseline of 3 applies.

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?

States a specific verb (look up) plus the exact resource types accepted (domain, IP address, network/AS number) and the service used (heade.rs), then enumerates the returned report categories. An agent immediately knows what it gets back and for which inputs.

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 clearly establishes the context of use: any time you need hosting, registration, DNS, email-security, certificate, tech-stack, AI-crawler, or port data for a domain/IP/AS. There are no sibling tools to differentiate from and no explicit when-not guidance, so this is clear context without exclusions.

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