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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so the safety profile is covered. The description adds value beyond that: the 'AS'-prefix stripping requirement for the input and the fact that results are paginated. It does not describe result ordering or page-size behavior, keeping it short of a 5.

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?

A single front-loaded sentence with a colon-delimited field list and a trailing 'paginated' qualifier. Dense and largely waste-free, though the field enumeration partially duplicates what the output schema already provides.

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 hints at them. For a 3-parameter read tool with one required input, the description plus annotations plus output schema cover everything an agent needs to call it 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 description coverage is 0%, so the description must carry the load. It does add the meaningful format constraint for asn_number ('without AS'), but page and limit are only gestured at by the word 'paginated' — no defaults or limits are restated, though the schema does supply defaults.

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 ('Get what the archive knows about') and resource (an autonomous system identified by ASN number), and enumerates the returned fields (organisation, total scans, unique URLs, first/last seen, BGP prefixes). This clearly separates it from the many other search_by_* siblings keyed on IP, favicon, JARM, nameserver, or registrar.

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?

It gives the crucial input-format rule ('ASN number, without AS'), which is actionable, but never states when to prefer this over alternatives such as search_by_ip or when a lookup would be empty. Usage is implied rather than contrasted, so it lands at the minimum-viable level.

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