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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering safety and idempotency. The description adds that results include decoded return codes, but does not disclose caching behavior, rate limits, or what constitutes a 'listing'—though the force_refresh parameter hints at caching. The description provides moderate additional context beyond the 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?

Two sentences, no wasted words. The first sentence states the purpose and target lists, the second describes the return value. Highly efficient and front-loaded.

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?

The description is concise but lacks details on the output structure (though an output schema exists), potential performance implications, or how 'decoded return codes' map to actual listing statuses. For a tool that queries multiple DNS block lists, it provides functional completeness but not operational depth.

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%, so the input schema already documents all three parameters with descriptions. The tool description adds no extra meaning to parameters beyond what the schema provides. Baseline 3 is appropriate when schema fully covers parameters.

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?

Description clearly states the tool checks domain reputation against specific DNS-based block lists (Spamhaus DBL, URIBL, SURBL) and returns listing status with decoded codes. This distinguishes it from similar tools like check_rbl, which typically check IP-based RBLs.

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 names the exact block lists, implying usage for domain reputation checks, but provides no explicit guidance on when to use this tool versus alternatives (e.g., check_rbl, check_mx_reputation). No when-not-to-use or prerequisite conditions are mentioned.

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