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

Annotations only say readOnly + openWorld; the description goes well beyond that by disclosing the underlying data source (Cloudflare 1.1.1.1 DoH), an important limitation (Cloudflare validates, this tool does not walk the chain to the root), and the x402 payment model with cost per successful call and no charge on failure. Those are exactly the operational facts an agent needs before invoking a paid, third-party-dependent lookup.

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 sentences, each doing distinct work: what is returned, how it is (and is not) validated, and what it costs. The most decision-relevant constraint — the chain-walk caveat — is placed immediately after the return description rather than buried.

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 in prose, and the remaining ambiguity (data source, validation depth, billing behaviour on failure) is fully covered. For a single-parameter read tool with annotations and an output schema, nothing an agent needs 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?

One required parameter with 100% schema description coverage, so the schema already carries the semantics. The description's mention that a URL is reduced to its host merely restates what the schema property says, adding no new parsing or formatting detail. 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?

The description states a precise verb+resource ("DNSSEC status for a domain") and enumerates exactly what comes back: AD flag, DS records in the parent zone, DNSKEY records with key-signing keys. It does not name or distinguish itself from near-neighbours such as agent_intel_ssl_certificate_transparency or agent_intel_domain_authority_credibility, so an agent must infer the difference from the resource name alone.

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?

Usage is implied by the subject matter — a caller looking for DNSSEC validation will recognise it — but there is no explicit "use this when..." statement, no exclusions, and no routing to sibling lookup tools (SSL CT, domain authority, typosquat radar). The pricing/payment note is the only practical precondition disclosed.

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