utilpeek: spell out a number in English words, or parse number words

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

Annotations already establish read-only/idempotent/non-destructive, and the description adds substantial extra context: half-even rounding to the minor unit, the 10^36 ceiling, 422 for invalid or out-of-range input (with no charge), typical latency under 0.3 s, price, and a 10-call free tier. That is exactly the beyond-annotation detail an agent needs.

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?

Front-loads the core purpose in the first sentence, then adds operational facts in dense but non-redundant clauses. Slightly packed with pricing/free-tier detail, though each sentence carries usable information.

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?

An output schema exists, so return-shape documentation is unnecessary; the description supplies input constraints, error behavior, performance, cost, and rate limits. Nothing needed to call this correctly is missing.

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 enum values and defaults are already documented; the description nonetheless adds real semantics such as half-even rounding for currency, the 13-currency scope, and the rationale that value must never be a float to avoid rounding surprises.

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 precise verb+resource pair (convert numbers to English words / parse number words back) and explicitly differentiates itself from the sibling convert_units. An agent can identify the tool's function and its boundary without opening the 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?

Explicitly routes unit conversion to convert_units and explains the two modes (to_words vs to_number) and when each applies. It lacks broader guidance on when this tool is preferable to other text utilities, but the key alternative is named.

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