rdap_lookup

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

With no annotations, the description carries the behavioral disclosure burden. It adds value beyond the schema by stating the return shape ('structured JSON responses'), the discovery mechanism ('Automatically discovers the RDAP server via IANA bootstrap'), and the failure behavior ('falls back with a clear error message'). It doesn't cover auth/rate limits, but for a read-only lookup this is noticeably transparent.

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?

Four sentences, front-loaded with purpose, and every sentence contributes distinct information: what the tool does, protocol context, server discovery, and limitation/error behavior. No filler or repetition.

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 single-required-parameter lookup with no output schema, the description covers the essential invocation context: purpose, output format, auto-discovery, and fallback error behavior. It is slightly short of a 5 because it doesn't hint at what fields the structured JSON contains or how the optional server override affects behavior, but those are minor for agent selection.

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?

All three parameters already have schema descriptions, so the baseline is 3. The description adds a little extra meaning by explaining the IANA bootstrap behavior behind the optional server override, but the timeout and domain parameters gain nothing beyond their schema text.

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 opens with a specific verb and resource: 'Look up RDAP information for a domain.' It further clarifies the protocol as modern successor to WHOIS. However, it does not explicitly contrast itself with siblings like whois_lookup or whois_raw, so it misses the top tier.

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 implies when to use it by explaining RDAP is the modern successor to WHOIS and warns that 'Not all TLDs support RDAP.' It does not explicitly name alternatives or state 'use whois_lookup for legacy/fallback cases,' so guidance remains implied rather than explicit.

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