check_mx_reputation

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds context about what is checked (RBLs and reverse DNS) and notes the distinction from check_rbl. With annotations present, this is more than sufficient, though it doesn't describe output format or rate limits.

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 exactly two sentences, both informative and front-loaded. The first sentence states the core purpose, the second adds usage guidance and sibling differentiation. No wasted words.

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 that an output schema exists and the tool is read-only with idempotent hints, the description covers the essential context: purpose, usage, and differentiation. It doesn't mention potential caveats like cache behavior (though force_refresh is in the schema), but for a simple read-only check, this is adequate and slightly above minimal.

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?

The schema description coverage is 100%, and all parameters (domain, format, force_refresh) are already well-described in the schema. The description adds no additional meaning beyond what the schema provides, so the baseline of 3 is appropriate.

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 checks MX IP addresses against spam blocklists (Spamhaus, Barracuda, SORBS) and verifies reverse DNS. It explicitly distinguishes from check_rbl, which checks a specific IP directly, providing clear differentiation from a closely related sibling.

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?

It provides explicit when-to-use guidance ('Use when you want to know if your mail server IP is blacklisted, or if your MX is on any blocklist') and names an alternative tool (check_rbl) with a clear distinction. This fully satisfies the criteria for usage direction.

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