Search urlscan.io history

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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is known. The description adds genuine operational context beyond that: it is passive, does not touch the target, and is safe to reuse during an investigation, plus it sketches the shape of the results (domains, IPs, ASN, links).

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?

The purpose and scope are front-loaded in the first sentence, and the routing advice follows immediately. Four sentences carry some phrasing that could be tightened, but each sentence contributes distinct information (purpose, alternatives, safety, returns).

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 an output schema present and full annotation coverage, the description needn't explain return values in detail, yet it still summarizes them. Purpose, alternative routing, safety, and query framing are all present, leaving nothing an agent needs to call this 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?

Schema coverage is 100%, so both parameters are fully documented in the schema, including query syntax examples and the size range. The description reinforces the Elasticsearch query framing but adds no per-parameter detail beyond what the schema already provides, so the 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 (Search) and resource (urlscan.io's historical scan database) and immediately frames scope with the Elasticsearch query syntax. It is clearly distinguishable from scan_url by emphasizing *existing* scans, so an agent can separate it from siblings without opening a 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?

Explicitly routes the agent: 'Call this to find *existing* scans instead of running a new one,' naming the alternative behavior (i.e. scan_url) and the condition that selects it. It reinforces with three concrete use cases (domain/IP history, favicon/TLS-cert hunting, shared-infrastructure discovery).

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