check_rbl

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

Annotations already cover readOnly, idempotent, non-destructive, and openWorld, so the safety profile is settled. The description adds real behavioral context beyond that: the tool first resolves MX hosts to IPs, meaning it implicitly depends on MX records existing and on live DNS queries to third-party blocklists. It omits caching behavior (implied only by the force_refresh param) and per-blocklist query 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?

Two tight sentences that front-load the core action and follow with the methodological prerequisite. Minor flaw: it claims '6' blocklists but enumerates only five (SpamCop, UCEProtect, Mailspike, Barracuda, PSBL), an internal inconsistency that wastes a little trust.

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?

With an output schema present and rich annotations, the description needn't explain return values, and it correctly covers the MX-to-IP resolution step an agent should know about. The remaining gap is behavioral edge cases (what happens with no MX records) and disambiguation from sibling reputation checks.

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 domain, format, and force_refresh are already fully documented with examples and rationale. The description adds no syntax or semantics beyond the schema; baseline 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 and resource (check IP reputation against DNS-based RBLs) and adds important scoping detail that the target is MX server IPs, plus the actual list of blocklists consulted. It is clear what the tool does, but it never distinguishes itself from the near-identical siblings check_mx_reputation, check_dbl, or check_realtime_threat_feed.

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?

There is no explicit when-to-use or when-not guidance, and no alternative is named despite several closely overlapping siblings (check_mx_reputation, check_dbl, check_realtime_threat_feed). The agent must infer from the name alone which of these overlapping reputation tools to call.

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