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

Annotations already declare readOnly, idempotent and closed-world behavior, so the safety profile is covered. The description adds genuinely new behavioral context: the supported magnitude (up to 999 trillion), support for the Indian lakh/crore system, and a sample of the output format.

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 use case and the core capability in two efficient clauses with a helpful example. The trailing web-page URL adds little operational value but is minor.

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?

With no output schema, the description carries the return-value burden and does so via the 'and 45/100 dollars' example plus the stated numeric range. Coverage is strong for a simple three-parameter converter, though a fuller output example would close the remaining gap.

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 baseline is 3. The description goes further by tying parameters to meaning: 'and 45/100 dollars' illustrates the unit/currency output for cheques, and 'Indian lakh and crore' explains what the system enum actually changes.

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 transform ('spell out any number up to 999 trillion') with a concrete output example ('and 45/100 dollars'), making the verb+resource unmistakable. An agent can distinguish it from siblings like roman_numeral_converter or number_base_converter without opening any 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?

Opens with a clear situational trigger ('Writing a check?') that tells the agent exactly when this tool is relevant, and notes the Indian numbering scope. However, it names no alternative tools or exclusions, so it stops short of full routing guidance.

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