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

Since no annotations are provided, the description carries the full burden. It discloses the core behaviors (forward resolution, IPv4/IPv6) and the safety intent (SSRF prevention), which implies a safe read-only operation. However, 'network routing verification' is somewhat vague, leaving some ambiguity about what exactly is verified. This is a minor gap given that it clearly indicates the operational scope.

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 with no filler: a clear action statement, a usage recommendation, and an explicit exclusion. The most critical information (what it does) is front-loaded, and every sentence serves a distinct purpose.

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?

For a simple one-parameter tool with no output schema, the description covers purpose, usage, and exclusions. It does not describe the return format or error behavior, but given the simplicity and the safety-focused use case, this is a minor omission. The description is sufficiently complete for an agent to invoke it correctly.

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%, so the schema already documents the 'domain' parameter. The description adds extra value by explicitly instructing not to include protocols or URL paths and emphasizing the FQDN format. This goes beyond the schema's basic type and format, improving the agent's chance of correct invocation.

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 function: 'Performs forward DNS resolution and network routing verification' and specifies it resolves IPv4 and IPv6 addresses. It also names the exact use case (SSRF guard) and explicitly differentiates from WHOIS and port scanning, making it distinguishable from any related tools.

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 gives explicit guidance on when to use it ('Use to verify host reachability and guard autonomous agents against SSRF before making HTTP requests') and when not to ('Do not use for WHOIS domain registration lookups or deep port scanning'). This is exemplary usage instruction.

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