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

With no annotations, the description must carry the behavioral burden, and it partially does: 'Pure CPU, instant' tells the agent there is no network dependency or latency cost, implying a safe, deterministic read-style operation. It omits other behavioral facts an agent would want, such as whether the output is a plain string and whether large or negative numbers are handled.

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 short sentences, front-loaded with the core action and followed by a useful performance note. Every clause carries information and nothing is padded.

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 two-parameter utility with no annotations and no output schema, the description covers the essentials but leaves two real gaps: no example of the returned string format, and no explanation of how the advertised ordinal form is requested given the schema only exposes number and currency.

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 adds only the notion that currency produces a currency-formatted spelling. Notably it advertises 'ordinal forms' although no ordinal parameter is declared in the schema, which adds information but leaves the mechanism for requesting an ordinal unexplained.

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 and resource (number to English words) plus two modifiers (currency, ordinal), which is far more informative than the name alone. It does not, however, distinguish itself from near-siblings like roman_numerals or convert_number_base, so an agent must infer the boundary.

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 when-to-use or when-not guidance and no reference to alternatives, despite several sibling tools (roman_numerals, convert_number_base, percentage) operating on numbers. The use case is inferable from the purpose sentence, but nothing routes the agent between competing tools.

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