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

With no annotations, the description carries the burden, and it does much of that work: it discloses cost ('free'), signals a read-only lookup, and names the return payload fields, which matters because there is no output schema. The gap is behavior when neither optional parameter is supplied (0 required params) — the description is silent on the default/all-tools case.

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 short sentences, zero filler: purpose and cost first, return contents second, parameter routing last. Nothing repeats the tool name or pads.

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 simple two-parameter lookup with no output schema, describing the returned fields is the key omission it correctly covers. It falls short only on the zero-argument case and error behavior for an unknown tool_name/url.

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 with examples in the schema; baseline is 3. The description adds only the either/or framing of the two lookup modes, which is a marginal gain beyond the per-field descriptions.

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+resource ('look up pricing for any code402 tool') and enumerates what is returned (pricing tiers, accepted networks, availability). No sibling tool does pricing, so it is trivially distinguishable from the chain_*/check utilities listed.

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 description disambiguates the two lookup modes ('use tool_name for named lookups or url for URL-based lookups'), which is genuine routing guidance at the parameter level. It does not say when an agent should call this versus just invoking a tool, nor any prerequisite such as 'check pricing before paid calls' — usage is implied rather than stated.

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