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

Annotations already cover the read-only and open-world profile, and the description adds genuinely new context: each call consumes one lookup against a monthly quota, and several returned fields (registry, allocation date, cloud provider, datacenter flag) are plan-gated. What it omits is failure behavior, e.g. what happens for a private or unroutable IP, which matters for an open-world 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?

A single front-loaded sentence that leads with the resource and then enumerates return contents per mode; the parenthetical "(by plan)" markers are compact qualifiers rather than filler. The return-field inventory is slightly list-heavy but every clause carries information.

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 only two parameters, no output schema, and no required fields, the description does most of the necessary work by enumerating what comes back for each input mode and noting the quota cost. The remaining gap is the absent statement that exactly one of ip/asn is needed, which is exactly the ambiguity a zero-required-parameter schema creates.

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 already documented, and the description only restates their accepted forms (public IPv4/IPv6, or an AS number with or without the "AS" prefix). It adds no guidance beyond the schema, such as precedence if both fields are supplied, 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?

The description names a specific verb and two clearly bounded resources: the ASN behind ONE public IP, or ONE network by its AS number, with concrete examples ("AS13335" or "13335"). The repeated emphasis on "ONE" implicitly separates it from bulk_lookup, but it never names lookup_ip, so the agent must infer the boundary with the closest sibling.

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 rather than stated: single-IP and single-ASN modes are described, which suggests it is not the bulk tool, but there is no explicit when-to-use/when-not or named alternative. It also never says the two parameters are mutually exclusive or that one must be supplied, leaving call routing to inference.

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