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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds genuinely new context: the exact return field set, the 1-credit cost per successful call, and the fact that schema-invalid input is rejected before billing. That billing-on-failure rule is exactly the sort of behavioral detail annotations cannot convey. It stops short of covering error responses for unknown codes (the 'known' field is only implicitly explained).

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 sentences, both front-loaded with the highest-value information: what you get and what it costs. The pricing sentence also encodes the billing exception, so no sentence is filler.

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?

Although there is no output schema, the description inlines the full return object shape, and the single parameter is fully documented in the schema. Cost, closed-world scope, and input validation behavior are all covered, leaving nothing an agent needs in order 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?

The input schema has 100% description coverage and already constrains code to 100–599, so the schema does the heavy lifting. The description's only added semantic is that 52x Cloudflare codes are in scope, which is a small but real extension beyond the plain range in the schema. Baseline 3 is appropriate.

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 the resource (an HTTP status code) and enumerates exactly what is returned: name, meaning, class, retryability and default cacheability. It even scopes the coverage to Cloudflare's 52x codes, so an agent knows this is the right tool for those non-standard codes. No sibling in the list overlaps with this lookup job.

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?

There is no explicit when-to-use/when-not-to-use guidance or named alternative, though the purpose is so narrow that usage is strongly implied by the tool name and description. The Cloudflare 52x mention at least signals the breadth of supported inputs, but an agent gets no routing instructions beyond that.

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