check_rbl

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the agent knows this is a safe read operation. The description adds valuable context: that it resolves MX hosts to IPs firstma and checks against a specific list of 7 blocklists. This goes beyond annotations but does not disclose potential rate limits or response structure. Given annotations cover safety, adding the resolution step and blocklist names is meaningful, so a 3 is appropriate.

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, front-loaded with the core action, and no filler. The second sentence adds a valuable implementation detail (MX resolution) and a concise list of blocklists. Every word earns its place.

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 tool is simple (one required param, three total). The description explains the core workflow (resolve MX to IPs, check against 7 blocklists). Output schema exists, so return format is covered. It could mention if there are rate limits or failure behaviors, but for a read-only lookup with clear paramschers, this is adequate. The only slight gap is no mention of what happens if no MX records exist, but that's minor.

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% (all 3 parameters have descriptions). The description does not add any parameter-specific semantics beyond what the schema already provides; it only explains the overall workflow. Per rubric, baseline is 3 when coverage is high, and there's no extra value, so a 3 is correct.

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 uses specific verb ('check'), resource ('MX server IP reputation'), and scope ('against 7 DNS-based Real-time Blocklists'). It clearly distinguishes from siblings like check_mx (which likely checks MX records/configuration) and check_mx_reputation (which may be similar but this tool specifies the 7 blocklists).

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?

No explicit guidance on when to use this tool vs alternatives, nor any prerequisites or exclusions. While the description makes the function clear, it doesn't contrast with check_mx_reputation or other related tools. The user must infer when this is the right choice.

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