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

Annotations already cover safety (readOnly, idempotent, non-destructive), and the description adds genuinely new behavior: batch limits of 1,000 IPs and 1,000 CIDRs, IPv4/IPv6 support, non-fatal handling of invalid entries, and per-call pricing via x402. The error-tolerance and cost disclosures are exactly the kind of context structured fields cannot convey.

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?

Three compact sentences: what it does first, then operational limits and error behavior, then price. Every sentence carries information an agent needs, with no filler or repeated title text beyond the lead.

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?

There is no output schema, yet the description explains the return shape (per-IP list of all matching ranges) and how failures surface (invalid entries reported, not fatal). Combined with limits and pricing, an agent has everything needed to call and interpret results.

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% and the schema already declares maxItems 1000, maxLength, and the array-or-delimited-string acceptance, so the description's restatement of the 1,000 limit is largely redundant. The only added semantic is IPv4/IPv6 support, which is not a per-parameter detail; baseline 3 fits.

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 states a specific operation — checking IPs against CIDR ranges and returning, per IP, every matching range — with both resource types named. This is clearly distinguishable from siblings like cidr_aggregate, cidr_split, or cidr_info without opening any 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?

The parenthetical '(allowlist / blocklist check)' gives a concrete usage context that tells an agent when to reach for this tool. It stops short of naming alternatives (e.g., cidr_info for range details) or stating when not to use it, so it lands at a clear but non-exhaustive 4.

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