rdap_lookup

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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and openWorldHint, so the safety profile is covered. The description adds the nature of RDAP as a WHOIS replacement and the shape of results, but says nothing about caching behavior, rate limits, or failure modes for unregistered domains. Adds moderate value on top of 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?

Front-loads the core action and keeps to a few tightly packed sentences with zero filler. The return-field list is somewhat enumerate-y but still earns its place by supporting purpose clarity.

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 annotations fully covering safety and idempotency, a complete input schema, and an output schema handling return values, the description supplies enough context to call it correctly. Minor gaps around caching/error handling keep it from a 5.

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%, so the schema already documents domain, format, and force_refresh with enum values and cache-bypass semantics. The description adds no parameter-level detail beyond what the schema provides, so the baseline 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?

States a specific verb and resource ('Fetch domain registration data via RDAP') and explicitly enumerates the returned fields (registrar, registrant, dates, EPP status, domain age). It names the sibling check_ns and clarifies the distinction, so an agent can tell it apart without reading schemas.

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?

Explicitly states when to use it ('who registered the domain, who the registrar is, or when the registration expires') and names the alternative to pick instead for nameserver questions ('distinct from check_ns which identifies the DNS nameserver provider'). Both the selection condition and the exclusion are present.

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