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

Goes well beyond the readOnlyHint/openWorldHint annotations: discloses the pricing model and mechanism (x402, $0.002 USDC, Base/Solana/Arc), that failed calls are free, data staleness, and the precise meaning of a known=false result. These are exactly the traits an agent needs before spending money on a call.

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 sentences, front-loaded with the core behavior, then caveats, then cost. Every clause carries decision-relevant information with no padding.

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, and the description still explains the one output nuance an agent must interpret (known=false). Combined with cost and staleness disclosure, nothing needed to call or interpret it 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?

Only one parameter with 100% schema coverage, so the schema already carries the load. The description confirms the address is IPv4 but adds no extra syntax or validation guidance beyond the schema's own example.

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+resource ('Lists the TCP ports Shodan has seen open on an IPv4 address') with the data source named. It also draws the key boundary against live scanning, so an agent can tell it apart from active exposure tools like security_ssh_banner_audit or security_rdp_exposure_check.

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 the passive nature ('nothing connects to the address now') and when results should be distrusted (record can be days old, known=false doesn't prove closed). It doesn't name a sibling to use for live/active checks, so routing guidance is implied rather than complete.

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