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

Goes well beyond the readOnly/openWorld annotations: it discloses the data source (Shodan pre-collected passive scan), the key semantic that absence means 'not seen' rather than 'closed', the fact that no traffic is sent, and the exact per-call price with billing rules for failures. Read-only annotation is consistent with the passive design; no contradiction.

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 tight sentences, front-loaded with the core fact, then caveats, then pricing. Nearly every sentence earns its place; the pricing detail is lengthy but operationally necessary for a paid x402 call.

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 probe with an output schema (so return format need not be explained), the description covers source, semantics, negative-result meaning, and cost. An agent has everything needed to call it and interpret results correctly.

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 (ip) and schema description coverage is 100%, with the schema documenting the IPv4 format and an example. The description adds no parameter-specific syntax or edge-case notes, so the schema carries the burden and 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 (reports) and resource (whether Shodan passive scan shows TCP port 53 open on an IPv4 address). Crucially, it explicitly carves out what the tool is NOT (not a recursive-resolver test, no query sent), which prevents the agent from misreading the name as an active resolver test — distinguishing it from active scanners like security_open_port_scanner.

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 tells the agent what question the tool answers and what it cannot answer, implying when it is useful (passive port-open facts) versus when it is not (recursion behavior). However, it never names a sibling alternative or says 'use X instead when you need recursion,' so selection guidance remains implicit.

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