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

With no annotations, the description must carry behavioral burden. It usefully discloses pricing ($0.001/call via x402 on eip155:8453), which is genuine context, but says nothing about return format, pagination of the limit param, or empty-result behavior.

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 compact sentences that front-load the resource definition before the usage modes. The appended pricing clause is slightly awkward but brief and earns its place as cost context.

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?

For a read-only reference lookup with no output schema or annotations, the description covers what is returned (phrase, category, explanation) and the two query modes, which is enough to call it correctly. Slightly more detail on limits/pagination would round it out.

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 the schema already documents code, category and limit. The description adds marginal value by framing the two lookup modes (specific code vs. whole category), which clarifies the code/category interaction, but no syntax beyond the schema's own enum and notes.

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 (look up) and resource (HTTP response status codes) plus the returned fields (phrase, category, explanation). The purpose is unambiguous, though it doesn't explicitly differentiate from any sibling, which is largely unnecessary given the unique resource.

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?

"Look up a specific code or list a whole category (1xx–5xx)" gives two implied usage modes and clarifies the code-vs-category choice. However there is no when-to-use/when-not guidance or named alternatives, leaving usage only implied.

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