DC5 Whois

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

Annotations already cover the safety profile (readOnly, idempotent, non-open-world), but the description adds materially more: the check is offline/instant with no DNS, registry or network call, and it catches script tricks only — not typos or digit swaps like paypa1.com — so a clean result is not a safety guarantee. That false-negative caveat is the kind of behavioral disclosure that changes agent behavior.

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?

Three tight blocks: what it detects with an example, when to use it and the sibling overlap, then behavioral limits. The scoping caveat and the sibling exclusion are both front-loaded rather than buried, and no sentence is filler.

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 single-parameter read-only checker with an output schema, the definition covers purpose, routing, offline behavior, and the false-negative boundary. Return values need only brief mention, which it provides ('scripts used and the Latin name it imitates'). Nothing needed to call it correctly is missing.

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% for the single parameter, so the schema already documents acceptable input (Unicode or punycode, no full URL). The description restates the same scope ('one domain or Web3 name') and the раураl.com example illustrates the tool rather than adding parameter syntax beyond the schema. 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 ('check') and resource ('one domain or Web3 name') and names the exact failure mode it detects (homograph / mixed-script look-alike) with a concrete example. It also implicitly separates itself from lookup_target, which is a sibling it explicitly references.

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?

Gives explicit use cases ('phishing triage, brand monitoring') and an explicit when-not: lookup_target already includes this warning, so there is no need to call both for one name. That is exactly the routing guidance an agent needs against a sibling.

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

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

Annotations already declare readOnly/openWorld/idempotent, but the description adds materially more: it reads public DNS only, never connects to the domain's mail servers, and therefore cannot test SMTP TLS, certificates or mailbox existence, plus a typical runtime under 2 s. That explicitly bounds what the tool cannot prove, which is the failure mode an agent is most likely to hit.

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 verb and scope, then usage, then behavioral limits. The long parenthetical enumeration of checks is dense but carries real scope information for a grading tool, so it mostly earns its space; it could be trimmed slightly without loss.

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?

An output schema exists so return values need not be explained, yet the description still tells the agent the grade levels (strong/fair/weak/no_mail/none) and that each check yields a status plus a one-line finding. Combined with the DNS-only limitation, an agent has everything needed to call it correctly and interpret results.

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?

Only one parameter and schema description coverage is 100%, so the schema already defines 'domain' including the 'not an email address and not a mail server host name' exclusion. The description adds nothing about the parameter beyond the schema, 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?

Specific verb ('Grade') plus resource ('one domain's email authentication') and an explicit enumeration of the checks performed (SPF, DMARC, MTA-STS, TLS-RPT, BIMI, DANE, null MX). It also defines the grade vocabulary, and explicitly says lookup_target gives only the overall grade, so an agent can separate it from the sibling without opening either schema.

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?

States the triggering contexts plainly ('questions about spoofing, deliverability or a DMARC rollout') and names the alternative tool plus the condition that should route to this one instead ('lookup_target gives only the overall grade; this tool gives the status and a one-line finding for each check'). Nothing is left to inference.

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

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

Annotations already declare readOnly, idempotent and openWorldHint=false; the description reinforces this with 'takes no arguments and makes no external calls', which confirms the closed-world/no-side-effect profile. It also names the per-dataset fields returned (state, record count, generation date, stale flag), adding useful context, though this overlaps with the output schema.

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?

Three compact paragraphs: dataset inventory first, then usage/routing, then runtime behavior. Front-loaded and every sentence carries information; no redundant filler.

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?

An output schema exists so return values need not be explained, yet the description still briefly names the fields, and it covers usage, exclusions and safety behavior. Nothing an agent needs to call this zero-arg tool correctly is missing.

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?

There are zero parameters, so the baseline is 4; the description's 'takes no arguments' is consistent with the empty schema. No additional meaning is required for this dimension.

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 (List) and resource (local datasets/feeds behind lookup_target) and even enumerates the dataset families covered (RIR, IANA, PSL, cloud/CDN, Tor, reputation, GeoLite2). It clearly distinguishes itself from lookup_target by scoping to the local, pre-loaded data rather than live lookups.

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 ('judge how current a reputation, RIR, cloud or geolocation answer is, or explain why such a section is missing'), and gives an explicit exclusion ('Registry, DNS and Web3 data are fetched live and are not listed here'). Nothing is left to inference.

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

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

Annotations already declare readOnly, openWorld and idempotent, yet the description adds real value beyond them: live registry/DNS/RPC queries, 1-5 s typical and ~12 s worst case, partial results with failures surfaced under errors, local-blocklist-only reputation with the explicit caveat that no match is not a clean bill of health, and no query logging.

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 dense paragraphs, front-loaded with the resource list and result summary before routing advice and behavior. Slightly long, and the per-resource fact-sheet enumeration borders on cataloging, but every sentence carries decision-relevant information.

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?

Output schema exists and the description still notes the trailing details_url provenance link. Combined with live-query timing, partial-failure handling and reputation caveats, nothing an agent needs to call this correctly or interpret the result is missing.

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 baseline is 3, but the description goes further by tying each accepted query form to the result shape the agent will get back (registrar/dates/DNS vs. network owner/ASN/geo vs. Web3 registration), which helps the agent decide what to pass. The namespace parameter itself is not discussed in the description, so it is not a full 5.

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?

Names a specific verb ('look up') plus every resource class it accepts (domain, IP, CIDR, ASN, Web3 name) and states the returned artifact ('compact fact sheet'). An agent can distinguish it from check_lookalike or check_mail_security without opening any schema.

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?

Gives explicit routing: 'use it first for any question about who owns, runs, hosts or registered something,' then names both alternatives with the condition that selects them (check_mail_security for per-check detail, check_lookalike for bulk screening without network calls). Both when-to-use and when-to-prefer-something-else are covered.

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